This is a delicious treat that requires no creaming together, and can be made in one pan. I bake mine in a flat bottomed roasting dish (no measurements to hand, I’m sorry! I use it to roast chicken and vegetables, if that helps). This is a tweak on Nigella’s Chocolate sheet cake and I’m so glad I found it. The recipe calls for buttermilk, but I make my own by adding the lemon juice to whole milk and leaving to stand for a while (you could use lime juice, white wine vinegar, apple cider vinegar instead. It’s the acid that curdles the milk). You could of course just use buttermilk if you prefer. Also, don’t expect this cake to rise much – it will end up being a brownie type, moist crumb. And the batter will be thin (double cream consistency) it’s supposed to be, so don’t worry! I’ve written this recipe as I like to read and follow them, but any feedback is welcomed!
1) Preheat oven to 180C (or 160C if oven is fab assisted. Your cake will need to go in the middle, so move shelves etc now if necessary.
2) Butter the tin, and line with greaseproof paper. Make sure you trim any that is taller than the top of the tin.
3) Measure 125ml of full fat milk into a jug, and add two teaspoons of lemon juice (or equivalent acid). Stir, and set aside.
4) To a large pan, add 200g cubed unsalted butter, 25g cocoa powder (proper cocoa powder please, not premade hot chocolate, it won’t taste good) and 250ml of water. Melt together over a medium heat, but do not let boil or get too hot. Once combined, take off heat.
5) in a bowl, stir together 300g plain flour, 200g caster sugar, a good pinch of salt, and a teaspoon of bicarbonate of soda.
6) Add two large eggs to your now curdled milk, and fork until incorporated together.
7) Add your dry mixture to your saucepan of gooey goodness and beat together – no need to be gentle, just tip the lot in at once (no sieving) and mix together. Once smooth, add the jugful of eggs/milk, and mix together. Add a teaspoon of vanilla extract (or seeds of a vanilla pod if you prefer) and mix again. Pour your loose batter into your prepared tin and pop into the oven (middle shelf). Set a timer for 17 minutes.
8) Meanwhile, add to a saucepan 50g cubed butter, 3 tablespoons of whole milk and two heaped tablespoons of cocoa powder. Do not hear yet. Measure out 150g of icing sugar (this will need to be sieved).
9) Test your cake after 17 minutes with a toothpick – if it comes out clean, it’s ready. If not, return to the oven and check every 90 seconds until it’s done. Put on the side to cool in its tin.
10) Turn on the heat for the saucepan and slowly melt together the milk, butter and cocoa. Once melted and smooth, add the sieved icing sugar, beating quite vigorously. Add a teaspoon of vanilla extract and mix again- it should be glossy and smooth.
11) Pour over your cake and spread evenly (the cake will still be hot and that’s fine). Add your choice of decoration (I like to use milk and white chocokatr buttons with some cocoa nibs strewn too, but you could use anything you like). Leave to cool and devour!