I think we’ve talked here before about how much I love sheet cakes. It’s all the flavour of a layer cake, but just way, way more laid back. They are super easy to transport (you just take the whole pan with you), are the best for loading up with sprinkles, and, I don’t know about you, but I LOVE making the swirls with my little offset spatula. I could seriously do it all day - it’s so relaxing to me.
Today’s recipe is a chance for me to love on the sheet cake just a little more, with this double chocolate situation. There’s a chocolate olive oil sheet cake on the bottom - it’s rich and moist, but still has a lovely springy texture, and a depth of flavour from the olive oil in the recipe. I then topped it with a fave of mine - milk chocolate german buttercream. Chocolate has got to be one of my all time faves when it comes to German buttercream. Someone once described it as room temperature ice cream, which I think is really just the perfect description. The chocolate goes so nicely with the silky buttercream, giving you this smooth, decadent topping to the cake. This cake would go great with a load of different buttercreams - in fact, there are a heap on the site here for you, but I can’t go past a good double chocolate pairing, and sprinkles are optional but also kind of necessary.
Let’s take a quick sec to talk about the oil I used in the recipe - I used the Robusto Extra Virgin Olive Oil from Filippo Berio. I love all of their oils, but the Robusto is great to use in baking where you really want the oil flavour to shine through. Here, it gives flavour, and the perfect texture to the cake, but also gives another dimension to the chocolate flavour of the cake, which is so perfect! If you wanted to have a slightly less intense olive oil flavouring, their Extra light olive oil is my go to for when I need a neutral oil in baking too. If you haven’t tried adding olive oil to your cake before, I highly recommend giving it a try!
A few wee tips:
I used a milk chocolate in the buttercream, which gave a very light taste, but if you wanted something a bit darker, sub the milk chocolate for a good quality dark chocolate.
Ideally the pastry cream for the German buttercream needs to chill down - I like leaving it for at least a few hours, or overnight if I can.
This cake is great as it comes together all in the one bowl - you end up with quite a bit of mixture, so make sure that you have a big enough bowl!
Chocolate Olive Oil Sheet Cake with Milk Chocolate German Buttercream
- Makes one 9” x 12” cake - serves 12-16 people -
Chocolate Olive Oil Cake
375g all-purpose flour
120g dutch cocoa
2 tsp espresso powder
1 tsp salt
1 ½ tsp baking soda
2 tsp baking powder
4 eggs, at room temperature
1 ½ tsp vanilla
180g Filippo Berio Robusto Extra Virgin Olive Oil
330g whole milk, at room temperature
300g freshly boiled water
Milk Chocolate German Buttercream
12g (1 ½ Tbsp) cornstarch
1 egg yolk
1 tsp kosher salt
190g whole milk
1 tsp vanilla bean paste
340g (3 sticks) unsalted butter, at room temperature
180g good quality milk chocolate, melted and cooled slightly
- PROCESS -
CHOCOLATE OLIVE OIL SHEET CAKE
Preheat the oven to 350°f / 180°c. Lightly spray a 9”x13” baking pan with baking spray, and line with parchment paper. Set aside.
In a large bowl, whisk together the flour, sugar, cocoa, espresso powder, salt, baking soda, and baking powder. Add the eggs, vanilla bean paste, Filippo Berio Robusto Extra Virgin Olive Oil, and milk, and mix to combine well. Add the boiling water and whisk until incorporated.
Transfer the batter into the prepared pan, and tap a few times on a flat surface to remove any excess bubbles.
Bake the cake for 40-45 minutes, until the centre springs back, or a cake tester inserted in the middle of the cake comes out cleanly.
Cool in the pan completely.
MILK CHOCOLATE GERMAN BUTTERCREAM
In a bowl, whisk together the sugar, corn starch, egg, egg yolk and salt. In a medium saucepan, heat the milk and vanilla to just shy of a simmer. Remove from the heat.
Using one hand to whisk constantly, pour half of the hot milk mixture into the egg mixture. This helps to temper the eggs and stop them from scrambling. Whisk until incorporated, and then pour the whole lot back into the saucepan.
Heat the milk and egg mixture over medium heat, whisking constantly, until it begins to bubble. It will thicken quickly. Once it has thickened, cook for one minute, then remove from the heat. Pour into a shallow container or bowl of a stand mixer and press some plastic wrap over the surface to avoid a skin from forming. Refrigerate until cold - at least four hours, preferably overnight. If you need to speed this process up, you can place the pastry cream in a bowl, then place the bowl in an ice bath. Stir frequently.
Fit your mixer with the whisk attachment, and place the pastry cream in the bowl. Whip the mixture on medium until creamy and lump-free. Begin adding the butter, a few cubes at a time, until fully incorporated. It may look curdled at some point but just keep whipping - it will come together! Once the buttercream is homogenous, add the cooled melted milk chocolate and mix to incorporate.
Transfer the cake to a serving plate or board. Dump the milk chocolate buttercream onto the cake, and, using an offset spatula, spread over the cake, creating swirls in the buttercream. Add sprinkles if desired.
Store leftovers in an airtight container in the fridge.
Thank you so much to Filippo Berio for sponsoring this post! All opinions are my own.