Brooklyn Blackout Cake

Ingredients

• For the cake
• 100g butter, at room temperature
• 260g caster sugar
• 2 large eggs
• 1/2 tsp vanilla extract
• 50g cocoa powder
• 3/4 tsp baking powder
• 3/4 tsp bicarbonate of soda
• 170g plain flour
• 160ml whole milk
• For the chocolate custard
• 500g caster sugar
• 1 tbsp golden syrup
• 125g cocoa powder
• 200g cornflour
• 85g butter, cubed
• 1/2 tsp vanilla extract

Instructions

1. Preheat the oven to 170 degrees / 150 degrees fan.
2. Line the bottom of two circular 20cm tins.
3. Cream together the butter and sugar until pale and fluffy. Add the eggs one at a time and mix well. Beat in the vanilla extract, cocoa powder, bicarb of soda and baking powder until well combined.
4. Add half the flour and half the milk and mix well. Repeat.
5. Pour 2/3 of the mix into one of the tins and the final 1/3 into the second tin.
6. Place the tin with 2/3 of the mix on the middle shelf of the oven and the tin with 1/3 of the mix on the shelf below it. Remove the smaller cake from the oven after 25 minutes or when a skewer comes out clean. Remove the larger cake after an additional ten or 12 minutes or when a skewer comes out clean.
7. Leave the cakes in the tin to cool. Then turn out onto a wire rack to cool fully.
8. Wrap the larger cake in cling film and place in the freezer to firm up.
9. In the meantime, make the custard: Put the sugar, golden syrup, cocoa powder and 600ml water into a large saucepan and place over a medium heat and slowly bring to the boil. Whisking occasionally.
10. Mix the cornflour with 160ml water, whisking while you add the water until. The mixture should be the consistency of thick glue. Gradually whisk the cornflour mixture into the cocoa mixture over a medium heat. You will need of arms of steel for this, the mixture gets stiff very quickly. Bring to the boil and simmer for a few minutes, whisking all the time until very thick. Remove from the heat and whisk in the butter and vanilla extract. Pour into a bowl and cover with clingfilm until very firm.
11. Assembly; Remove the big cake layer from the freezer, using a serrated knife, slice a thin layer off the top of the cake. Place this into a food processor and process until it is fine crumbs. Using the serrated knife, slice the remaining cake into two horizontally.
12. Take the cake board you are going to use and place a few tablespoons of the custard in the middle. Take three rectangles of greaseproof paper and place around this (this will help keep the board clean) Place the small layer on top of the board. Take about a 1/4 of the custard and using a spatula, spread it evenly around the top. Add a second layer of cake. Spread a similar amount of custard evenly on top of this layer. Add the final layer of cake. Spread the remaining icing around the cake with a spatula. Once the custard is smooth, using your hands press the cake crumbs on to the custard. Carefully pull the greaseproof paper out from underneath the cake. Place in the frige for about 2 hours to firm up.