The perfect custard square recipe - sheets of crisp homemade puff pastry sandwich a creamy rich vanilla bean custard. The whole thing is then loaded up with a vanilla bean icing. Custard Slice is a delicious take on a classic New Zealand childhood favourite.
Table of contents
- Custard Square with Homemade Puff Pastry
- Components of a Custard Square
- What is Custard Powder?
- How to Break Up the Workload for Custard Square
- Puff Pastry vs Rough Puff Pastry
- Steps for rolling out Puff Pastry.
- How to make small batch custard square
- Custard Square with Store Bought Pastry
- FAQ for Custard Square
- Recipe for Custard Square
Custard Square with Homemade Puff Pastry
Hi! Just popping in to share this recipe with you for Custard Square. Often also called Vanilla Slice in Australia, Custard square is two layers of puff pastry, surrounding a creamy, smooth custard. The whole thing is then topped off with a vanilla bean icing. It's a New Zealand Classic, and something I always used to get from the bakery growing up. Making custard slice from scratch takes a little more effort, but it is so, so worth it. Whether to you it's a custard square, a custard slice, or a vanilla slice recipe, it's just the best.
Components of a Custard Square
Custard square can be a wee bit labour intensive, but it is always, always worth it, and i'll pop a few shortcut steps along the way to help you out!
- Puff Pastry - I used a recipe from my friend Erin's book to make puff pastry from scratch, but you can do a rough puff, or you can use storebought pastry too. I'll add in tips in the FAQ section!
- Custard Filling - The filling of a custard square is a rich, creamy, set vanilla bean custard. I used custard powder for mine which I get online or sometimes can find in grocery stores in the US. I use it quite often in recipes that call for custard!
- Vanilla Icing - You can either ice these with a simple vanilla icing, or you can skip it and finish these with a bit of powdered sugar if you would like.
What is Custard Powder?
Custard Powder is similar to what is used to make instant pudding here in the states. It is corn starch based, then uses other flavours and thickeners. The taste is super nostalgic so I used it in these custard squares. You can grab some online - I use it to make my Nanaimo Bars too! If you can't find you should be able to sub corn starch. I haven't tried it but it should work just fine.
How to Break Up the Workload for Custard Square
Homemade Custard Slice is a little labour intensive if you choose to make your own puff pastry, but here is a good way to do it if you would like to break up the workload:
- Day one - make the puff pastry, wrap tightly and store overnight in the fridge.
- Day two - Bake the puff pastry sheets, make the custard filling, assemble the custard square, and chill overnight.
- Day three - Finish off custard square with icing and serve.
Alternatively you can do day two and three all in one day - the custard square needs about 4 hours to set up and chill down in the fridge.
Puff Pastry vs Rough Puff Pastry
I used a homemade puff pastry for these custard squares. It is a little labour intensive but once you get the hang of it, it is super fun and simple to make. The recipe comes from my friend Erin's book (she has a new one out VERY soon and it's amazing), and you can watch a great video here of her making it. The puff pastry recipe here makes enough for two batches of the custard squares, so you can store some pastry wrapped tightly in the freezer for another time.
I haven't tried this recipe with rough puff, but I am sure that it would work just fine! Rough puff pastry is made by just incorporating the butter into the pastry and then performing folds, rather than locking in a butter block like you do with a traditional puff pastry. Erin also shows that recipe in the same video! (Skip to about 22:30 for it!, and do 1 ½ or double the recipe. You need 700g pastry approx for this recipe)
Steps for rolling out Puff Pastry.
There are a few steps for making puff pastry. It does take a little time but the actual hands on time isn't too bad - just lots of chilling time!
- Make the dough, and make the butter block, and chill both down.
- Roll out the dough and 'lock in' the butter block
- Perform four folds (explained in the recipe)
- #1: 4-fold turn
- #2: 3-fold turn
- #3: 4-fold turn
- #4: 3-fold turn
- Then the pastry gets rested in the fridge until it is baking time, or stored in the freezer until you are ready!
How to make small batch custard square
I tested a small batch custard square with this recipe and it worked just great. I used a 9x5" loaf pan and worked out quantities needed using my pan size calculator. I did 0.56x the recipe needed and just calculated it that way. Instead of scaling the egg I just did one egg and one yolk.
Filling quantities for a 9x5" loaf pan are:
- 405g whole milk
- 265g heavy cream
- ½ tsp vanilla
- 40g custard powder ( I upped this just a little as it could have been a tiny bit firmer)
- 112g sugar
- 1 egg plus 1 yolk
- 40g unsalted butter
For the icing:
- 210g powdered sugar
- 25g unsalted butter
- pinch of salt
- ¼ tsp vanilla
- whole milk to mix
Please note that those are just the quantities that worked for that exact pan! The custard layer was a teeny bit thicker but worked great. The good thing about this recipe is that you can just pop extra custard into another bowl and have with some of the pastry scraps!
Custard Square with Store Bought Pastry
This can absolutely be made with store bought pastry - I tested it recently and it worked just fine. Just ensure that you have rolled out the pastry enough to account for any shrinkage when it bakes. You will need about 700g of pastry for a full batch of custard square. When I tested it with the small batch I used a 500g packet and had a little left over / probably could have rolled it a little thinner. It is much better to have a little too much pastry than not enough! Watch the bake time as it may be different with a different pastry - mine was done in 35 minutes then I gave it a further 5 minutes with the top tray off. To use store bought pastry, follow the steps from 12-16 for the pastry recipe.
FAQ for Custard Square
You can absolutely use store bought puff pastry in this recipe. - you will need about two sheets. Just make sure it is rolled out to a square about 12"x12" so that you have enough to fill the tin - it shrinks a lot when baked. I do encourage you to try making your own - I promise it is much less scary than it looks!
It needs AT LEAST 3-4 hours to chill. You need the custard to be completely set and cold right throughout. If you cut into it before it is properly chilled, you're going to have a bad time.
I found that when making my own pastry, obsessively squaring off the edges helped, along with measuring the temperature of the butter and the dough before I started the folds to ensure that they were a similar temperature.
Use a bread knife. Gently saw the top layer to cut through, then you can cut through the rest of the custard square. It might seem wobbly, but if your bread knife is sharp, you will be fine.
For more Custard Recipes, Check out:
- Brioche Custard Buns
- Chelsea Buns
- Paris Brest with Spiced Apple
- Roasted Strawberry and Custard Brioche Doughnuts
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Recipe for Custard SquarePrint
The perfect custard square - sheets of crisp flaky pastry sandwich a creamy rich vanilla bean custard. The whole thing is then loaded up with a vanilla bean glaze. This is a delicious take on a classic New Zealand childhood favourite.
Puff Pastry - Butter Block
- 450g unsalted butter, at room temperature
- 70g Bread Flour
Puff Pastry - Dough
- 400g bread flour
- 200g All-purpose flour
- 1 ½ tsp fine sea salt
- 115g unsalted butter, at room temperature
- 1 tbsp vanilla bean paste (optional)
- 290g cool water
Vanilla Bean Custard
- 720g whole milk
- 480g heavy cream
- 2 tsp vanilla bean paste
- pinch of Salt
- 65g custard powder
- 200g sugar
- 3 eggs, at room temperature
- 70g unsalted butter, at room temperature
Vanilla Bean Icing
- 375g powdered sugar, sifted
- 45g unsalted butter, at room temperature
- ½ tsp vanilla bean paste
- whole milk to mix (a few tablespoons)
- Cut a piece of parchment paper so it measures approximately 13 x 18 inches. (I use pre-cut sheets which are this size). Position with the short side facing you.
- In a medium bowl, place the butter and flour. Mix vigorously using a silicone spatula. Spread onto the bottom third of the parchment paper, and use an offset spatula to spread into a rectangle 6"x9", and ½" thick. Carefully square off the edges. Wrap in the parchment paper, and place in the fridge to firm up.
- In the bowl of a stand mixer fitted with the dough hook, combine the bread flour, all-purpose flour, and salt. Add the butter and vanilla, and mix on low until the butter is fully incorporated into the mixture. Add the water, and mix until a dough forms, 5-6 minutes. Increase the speed, and mix on high for 2-3 minutes until smooth.
- Turn out onto a piece of plastic wrap, and pat into a rectangle with your hands. Wrap in the plastic and rest in the refrigerator for 40-50 minutes.
- Once the butter and the dough are a similar temperature (16˚c / 60˚f to 21˚c / 70˚f), remove both from the fridge. On a lightly floured surface, roll the dough out to a rectangle 12" x 10", taking time to carefully measure, and squaring off the edges using a bench scraper if necessary. (This will make doing the folding much, much easier). Orient the rectangle so that the short side is facing you.
- Using the paper as a guide, peel back half of the parchment on the butter, and place on the bottom half of the dough, leaving a ½" margin around the edges. Fold the top half of the dough down over the butter block, pressing firmly around the edges to seal, and tuck any excess dough underneath the block. Wrap the dough tightly in plastic, place on a baking sheet lined with parchment, and rest in the refrigerator for approximately 30 minutes.
- Turn #1: 4-fold Remove the dough from the fridge, and unwrap. On a lightly floured surface, roll out to a ½ inch thick rectangle that is 13" wide and 19" long. If it is too warm and is becoming sticky, return to the fridge for a little more rest time. If it is too hard, allow to sit at room temp to soften a little. 30 minutes worked well for each rest time for me. Square off the edges. Turn the dough so a long edge is facing you. Take the left edge of the dough, and fold ¾ of the way across the dough, lining up the edges. Fold the right edge to meet the left, about ¼ of the way across. Fold the dough in half, left side over right. Transfer to the baking sheet, brush off extra flour, and cover with plastic wrap. Rest for another 30 minutes.
- Turn #2: 3-fold Remove the dough from the fridge. On a lightly floured surface, repeat the rolling process - roll to 13" x 19", and square the edges. Turn so a long edge is facing you. Fold the left side of the dough ⅓ of the way across, then fold the right side of the dough over the left (so you have 3 layers of dough). Place on the baking sheet, brush off flour, cover and refrigerate. Rest for 30 minutes.
- Turn #3: 4-fold Repeat the process for a 4-fold as explained above, taking care to square the edges. Cover and rest for 30 minutes.
- Turn #4: 3-fold Repeat the process for the first 3-fold. This is your final fold. Roll out, square off, and repeat the instructions for a 3-fold above. Cover, and rest for at least 30 minutes or up to overnight.
- At this stage the dough is ready to be used - cut in half, and store the dough either wrapped tightly in the fridge (you will use one half for the custard square and you can keep the rest for another project), or in the freezer.
- To make the pastry sheets, preheat the oven to 180c / 350˚f. Line two baking sheets with parchment paper. Take 700g of the prepared pastry (one half of the recipe above), and divide the piece into two. Wrap half in plastic and place in the fridge until needed - you will do this in two batches.
- On a lightly floured surface, roll out the first piece of pastry into a square that measures 11" square - this allows for shrinkage. Place onto the prepared baking sheet, and top with a second piece of parchment paper, then place a second baking sheet on top, to help prevent rising.
- Prepare the second piece of pastry the same way. Alternatively if you do not have enough baking sheets you can bake these one at a time and just repeat the process twice.
- Place the baking sheets in the oven, and place something heavy such as a cast iron skillet on top of the second baking sheet. Bake the pastry for approximately 40 minutes, switching half way through, or until golden brown. Remove the top baking sheet, and parchment paper, and bake uncovered for a further 5 minutes. Allow to cool slightly on the baking sheet, before transferring to a wire rack to cool completely.
- Using a sharp knife and the tin you are planning on using as a guide, trim the pastry squares so that they are the same size as your tin (I used a 9" square tin). Set aside until ready to assemble.
VANILLA BEAN CUSTARD
- In a large heavy bottomed saucepan, place the milk, cream, vanilla paste and salt. Heat over medium heat, until it is very hot to the touch and just shy of a simmer.
- Meanwhile, while the milk is heating, place the custard powder and sugar in a medium bowl, and whisk to combine. Add the eggs, and whisk until well combined and slightly pale in colour.
- Once the milk mixture has heated, remove it from the heat, and, whisking constantly, pour half of it into the egg mixture. Whisk well to combine, before adding the rest of the milk and whisking very well. Wash and dry the saucepan, and return to the stove. Strain the mixture back into the saucepan, and place over low to medium heat. Cook for 10-15 minutes, whisking constantly, until the custard is very thick. Remove from the heat and add the butter a small piece at a time, whisking to incorporate before adding the next piece.
- Use immediately for assembly.
- Line a 9" square tin with two sheets of baking paper, extending over the sides of the tin to act as a 'sling'. Place the first piece of puff pastry in the bottom of the tin, trimming slightly to make it fit if needed.
- Pour the hot custard over the top of the puff pastry, and smooth with an offset spatula. Place the second piece of pastry on top, pressing down lightly to ensure there are no air bubbles. Cover the tin with plastic wrap, and place in the fridge to set for at least 3-4 hours, or up to overnight.
- Once the custard has set, carefully use the parchment paper to remove the custard square from the tin, and place on a chopping board or large plate.
- Combine the powdered sugar, unsalted butter, and vanilla bean paste in a medium bowl. Add enough milk to reach a spreadable consistency (I used just over 3 Tbsp), or the desired consistency. Add more if you like a more glaze-like icing and less if you would like to make swoops in your icing.
- Spread the icing over the surface of the custard square, then place briefly in the fridge to allow the icing to set.
- Once the icing has set, cut into 16 squares using a bread knife which has been run under cold water and then wiped. Use a careful sawing motion. Serve immediately, or refrigerate until ready to serve. Best served slightly cold, on the day or the day after they are made.
Store leftovers in an airtight container in the fridge.
Pastry Recipe, with permission, from The Fearless Baker
Keywords: Custard Square, Vanilla Slice, Puff Pastry, Rough Puff Pastry