50g unsalted butter , softened, plus extra for the tin
2 tsp espresso powder , dissolved in 2 tsp hot water, plus extra for the tin
100g chocolate (70% cocoa solids), broken into squares
45g Bournville bar , broken into squares
50g golden caster sugar , plus 1 tbsp
1 large egg , separated
seeds from ½ a vanilla pod , or 1/2 tsp vanilla extract
4 tbsp plain flour , sifted
4 tbsp golden syrup
coffee or vanilla ice cream, to serve
STEP 1Heat oven to 180C/160C fan/gas 4. Butter four wells of a muffin tin, and sprinkle some espresso powder into each.
STEP 2In a pan, gently melt half of each of the chocolates with the butter until smooth. Stir in 50g sugar, then take off the heat and cool for a few mins. Stir in the coffee, egg yolk, vanilla and flour until even.
STEP 3Beat the egg whites with electric beaters or a balloon whisk until foamy and thickened. Add 1 tbsp sugar and whisk until it forms shiny soft peaks. Take care not to overwhisk – softer is better if you’re not sure.
STEP 4Stir about 1/3 of the egg whites into the chocolate batter to loosen, then carefully fold in the rest of the whites using a large metal spoon or a spatula.
STEP 5Spoon into the prepared tin, then bake for 10-12 mins or until the cakes are just starting to dome in the middle. Cool the cakes in the tin for 15 mins. In a small pan, melt the remaining chocolates and golden syrup together with 3 tbsp hot water, and whisk until silky smooth. Turn out the cakes and serve warm in a puddle of the syrup and topped with ice cream.