This is the chocolate sheet cake to end all sheet cakes. Guaranteed to be a hit at your kids birthday party, or when you need to feed a whole bunch of people with an easy and pretty cake that looks like you put a lot more effort into it than you actually did.
Plus this cake is so quick and easy to frost – no turntables or icing bags needed – which is fantastic if you are in a rush. And who isn’t these days?
The inspiration for this cake comes from the office where I work. We (much like every other office ever) have a birthday tradition, which involves my colleagues and I having to buy a shed-load of cake for all 75 people who work there every year on our respective birthdays. Cake for 75 people is A LOT, and as such more often than not my co-workers and I will bring in sheet cakes, purchased from one of the various supermarkets in town.
The chocolate sheet cake is well-known to be my absolute favourite, and it usually comes sprinkled with various chocolate candies, like the Rolos and Maltesers you see before you.
I’ve been meaning to re-create the iconic chocolate sheet cake for myself for a long time, and I’ve finally managed to find some time to get in the kitchen and do it, between printing wedding invitations and dealing with budget spreadsheets (wedding spending is getting a little out of hand…).
If you are used to making normal sponge cakes, then the process of putting this chocolate sheet cake together is going to leave you feeling a little bit, well, weird. This is not a normal cake recipe by any stretch of the imagination. At one point the mixture will look and feel like wet sand, and not long after that you will find yourself pouring what you will assume is too much coffee into the mixing bowl. How on Earth is this cake not going to taste like coffee? Have I misread the recipe? This batter looks too runny to ever actually turn into a cake, surely?
Don’t freak out. The cake will definitely taste like chocolate, without a hint of coffee to be tasted. I hate coffee, and I wouldn’t let this recipe anywhere near my blog if I wasn’t 100% convinced that all coffee-haters would love it as much as I do. No, you haven’t misread the recipe. It does ask for 225ml (one whole cup) of black coffee. It will mix in there, I promise. And yes, the super-runny batter will bake itself into a gorgeous soft and fluffy sheet cake, given 25 minutes in the oven.
And my god, is this cake soft. It is like eating a chocolate flavoured pillow. Its soft moist texture comes from the sheer amount of liquid going into the batter, as well as the use of melted butter.
My birthday is a long way off (thank heavens) but when it does roll round again, I am definitely going to be swapping the usual store-bought monotony for this best ever chocolate sheet cake. And I think everyone at work is going to be so glad I did.
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- 225ml (1 cup) strong black coffee (I used instant coffee)
- 120g (½ cup) unsalted butter
- 250g (2 cups) plain or all-purpose flour
- 300g (1½ cups) golden or white caster sugar (US granulated sugar)
- 1 teaspoon bicarbonate of soda (baking soda)
- ½ teaspoon salt
- 50g (1/3 cup) cocoa powder
- 2 large eggs
- 60ml (¼ cup) full-fat Greek yoghurt
- 60ml (¼ cup) whole milk
- 1 teaspoon vanilla extract
- 200g (¾ cup + 1 tablespoon) unsalted butter, at room temperature
- 75g (2/3 cup) cocoa powder
- 375g (3 cups) icing sugar or powdered sugar
- 75ml (1/3 cup) milk
- A handful of Rolos, Maltesers, or other chocolate candy to decorate (I also used chocolate curls, honeycomb pieces, and 50g of drizzled melted white chocolate)
- Preheat the oven to 190°C / 375°F (170°C fan) and line the bottom of a 9x13 inch baking tray with greaseproof paper or baking parchment. Make 225ml of strong black coffee using boiling water, and then set aside to cool whilst you make the cake. Melt the butter in the microwave, stirring regularly, and then also set aside to cool slightly.
- Put the flour, sugar, bicarbonate of soda, salt, and cocoa powder into a bowl, and mix well until combined, using a stand or hand-held electric mixer on a low setting. Add the melted butter and mix until combined. You will probably need to use a spatula to scrape down the sides and the beater during this process. You will eventually end up with a mixture that resembles wet sand.
- Add the eggs, yoghurt, milk, and vanilla extract, and beat well on a low setting. Once fully combined, pour in half of the coffee you made earlier and mix on low until combined. Add the remaining half of the coffee and mix again. The batter will be very runny, but this is okay.
- Pour the batter into the pre-lined tin, and bake in the pre-heated oven for 20-25 minutes, until a skewer or toothpick inserted into the middle of the cake comes out clean. Place the tin on a wire rack and leave to cool completely. Once cooled, the cake may look a little over-cooked, but it isn't burnt, I promise!
- Once the cake is completely cool, make the buttercream. Cream the butter with a hand or stand mixer until it is pale and creamy, and no lumps remain. Add the cocoa, icing sugar, and milk to the butter, and mix well until fully combined. Scrape down the sides of the bowl and mix again. Spoon the buttercream onto the sheet cake, and then spread evenly over the cake using an offset spatula or knife. Make sure the buttercream gets all the way to the edges. Drizzle melted chocolate over the top of the cake (optional) and top with the chocolate candies or decorations of your choice.
- This cake will keep for 3-4 days if stored in an air-tight container. There is no need to refrigerate, as this will dry out the cake more quickly. It will keep better before it has been cut into squares. The un-frosted sheet cake can be frozen for 2-3 months, and then defrosted at room temperature. The frosting can also be frozen for 2-3 months - just defrost overnight in the fridge and then use immediately.