Hi there. I'm so sorry I've been a little slack getting recipes up here for you. Our gas to our building has now been out for 3 weeks, and for someone like me, this is the biggest pain in the ass. I'm just wondering how long before I can ask our landlord to buy us an electric oven - because this is starting to get ridiculous. Coupled with a cheeky Kidney infection I managed to get (I've been prone to them since I was a baby, would not recommend!), things have been a little quiet.
I have however been managing to get by - my little countertop convection oven has saved my butt big time - it can fit 3 six inch cake tins, a pie tin, and a 9"x13" baking tin, (not all at once), so as long as things are able to be made in vessels of those dimensions, we are set.
Seeing as we are right in the thick of rhubarb season I figured it was only fair that I dropped another rhubarb recipe into the mix with this Rhubarb Frangipane Slab Pie. I had big plans to use one of Julie's recipes as the base for this tart, as I have been dying to try her method for the longest time, but got intimidated by braiding short crust pastry, so stuck to pie dough, which I am much more comfortable with. However I did discover that baking a slab pie in a removable bottom tart tin is a game changer - so, so easy to pop out, and the fluted edges make it super easy to trim the pie dough flush with the edges. Slab pies are my new fave - they are easy to make, and perfect for a crowd. Expect to see a lot more of them around here.
I went with my usual pie dough recipe, sweetening it up just a touch, then filled the bottom with a frangipane - a sweet paste made with ground almonds, egg, sugar and butter. The frangipane was then topped with some rhubarb, which I had previously roasted to help remove some of the moisture and add a little sweetness to. I then topped the whole thing off with a decorative lattice crust, and it was baked off. Each element complimented the other perfectly - the flaky pie crust, the nutty sweet frangipane, and the tart rhubarb. It's definitely going to be made around here again before rhubarb season is up.
A few wee tips:
- I made this in a tart pan with a removable bottom, but you could make it in a jelly roll pan or quarter sheet pan too.
- The pie dough is best if you can give it an overnight rest before using.
- The Rhubarb can be roasted ahead, and the frangipane can be made ahead of time if needed, too.
- I used pie stamps to make the shapes on the top of this - they are from Williams Sonoma and Amazon. They are my fave things - they make the pie look so fancy with little effort, and are great for using up scraps.
- When I roll out pastry for stamping, I like to pop it in the freezer for about 5 minutes to allow it to firm up slightly, so I can cut out a nice sharp stamp shape.
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A note on salt and oven temperature
It is important to note the type of salt that is called for in a recipe. I use Diamond Crystal salt throughout my recipes - if you use a different sort of kosher salt or regular table salt you will need to adjust accordingly as some salt is 'saltier' than others. Morton's salt is twice as salty, so you will need half the quantity. Same goes for a regular table salt. I am working to get gram measurements throughout my recipes for salt but still getting there.
All oven temperatures are conventional unless otherwise stated. If you are baking on fan / convection, you will need to adjust the temperature. An oven thermometer is a great investment to ensure that your oven is the correct temperature.
Using the double / triple function in the recipe card
You will notice that there is a '1X' '2X' '3X' button in my recipe card. This can be used for doubling or tripling a recipe. However, please note that this only doubles the ingredient quantities in the ingredients list and NOT in the method. If there are quantities or pan sizes in the method of the recipe (for example weigh out 150g brown butter), you will need to scale this number manually. It will also not change the baking time in the recipe so you will need to adjust this yourself too. It is always a good idea to read through a recipe fully before doubling it just to check this. If you would like to scale this recipe or convert for another pan size, use my calculator!
Tools and equipment
For a list of my go-to tools and equipment, I have a post you can refer to here.
Why is this recipe in grams?
I post my recipes in grams as it is the most accurate way to bake. Cups are not only inaccurate but they vary in volume worldwide. There is no way for me to provide one cup measure that works for everyone. However, posting in weight fixes this issue. If you would like the recipe in cups you are welcome to convert it yourself via google, but please do not ask me to do it for you as I am not comfortable providing a recipe using a method that I have not tested. Baking with a scale is easy, accurate, and also makes cleanup super simple. Here is the scale that I use if you would like a recommendation! Here's to accurate baking!Print
Rhubarb Frangipane Slab Pie
- 3 ¾ cups (470g) Flour
- Pinch of Salt
- 3 tsp (8g) sugar
- 3 sticks (340g) cold butter, cut into cubes
- 1 cup (240ml) cold water
- 1 cup ice
- ¼ cup (60ml) Apple cider vinegar
- 900g Rhubarb, trimmed and chopped into 10cm pieces
- 1 Vanilla bean, or 1 tsp vanilla bean paste
- 200g (1 cup) sugar
- ½ cup water
- pinch salt
- 140g unsalted butter, at room temperature
- 160g sugar (¾ cup)
- 200g almond meal / almond flour
- 2 eggs, at room temperature
- 1 tsp vanilla bean paste
- pinch salt
- 1 egg whisked with 1 Tbsp water
- Raw / Turbinado Sugar for Sprinkling
- Place flour, sugar and salt into a large bowl. Cut butter into chunks, and add to the flour. Toss lightly to coat. Working quickly, using a pastry blender or your fingers, cut the butter into the flour mixture until there are only pea-sized chunks left. You want a few lumps of butter remaining to keep the pastry nice and tender.
- Combine ice, water and cider vinegar in a bowl. Sprinkle a few tablespoons of the ice water into the flour and butter mixture, and using a stiff spatula or your hands, mix in well. Continue adding water a tablespoon at a time ( I normally need about 10-12 tbsp) until you have a dough that holds together well, but is not too wet. Squeeze together with your fingertips to make a homogenous dough. Shape into two rectangles, one slightly larger than the other, and wrap in plastic wrap. Rest in the fridge for at least two hours, or preferably overnight.
- Preheat the oven to 350˚f / 180˚c. Arrange the rhubarb in a 9" x 13 baking sheet. Split the vanilla bean lengthwise using a sharp knife, and nestle in the rhubarb. Combine the sugar, water and salt in a small bowl until the sugar has dissolved, and pour over the rhubarb.
- Bake for 20-25 minutes, until the rhubarb is just tender. Remove from the oven and cool. Remove the rhubarb from the syrup, and place on a paper towel to drain. Reserve the syrup - it is perfect for cocktails or soda!
- In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugar until just combined. Add the almond meal, egg, vanilla, and salt, and mix until incorporated. Set aside until required.
ASSEMBLY AND BAKING
- Roll out the smaller rectangle of dough until it is approximately ⅛" (3mm) in thickness. Line an 11" x 8" removable bottom tart tin with the dough, trimming any overhang flush with the edge of the tin. Keep any scraps and re-roll to use for decoration - I usually use these pieces for pastry stamps
- Using an offset spatula, spread the frangipane evenly in the bottom of the lined pie tin. Top with the roasted rhubarb, pressing down gently on the pieces.
- Roll out the second rectangle of dough, and cut strips to be used for a lattice. Lattice however you like - for this one I did a range of different width strips, cut with both a straight cutter and a fluted cutter, and incorporated some braids into the lattice too. Keep any scraps to use for stamping if desired.
- Place the finished pie in the fridge for at least 30 minutes. While the pie is resting, preheat the oven to 425˚f/ 220˚c. Place a baking tray on the bottom rack of the oven.
- Brush the pie with egg wash, and sprinkle liberally with raw sugar. Bake at 425˚f / 220˚c for 20 minutes, or until the pastry is set and beginning to go golden. Reduce the temperature 375˚f / 190˚c, and bake until the pastry is deeply golden and the filling is bubbling.
- Remove from the oven and cool on a wire rack. Serve warm or at room temperature.
Frangipane adapted from The Brick Kitchen