6 eggs, separated
6 heaped tbsp. flour
6 even tbsp. sugar
1 generous pinch of baking soda
for the cream:
2-3 tbsp. custard powder
1 pint warm milk
6 tbsp. sugar
100 gr butter
1 heaped tbsp. cocoa powder
Pre-heat the oven to 180 C. Line a round cake tin with baking parchment. For the sponge beat the egg white until very stiff (you can upturn the bowl and it still stays in). In a separate bowl beat the egg yolk with the sugar. Add the flour and baking soda. Fold in the egg white. Pour the mixture into the tin and bake for 20-30 minutes, until a wooden skewer inserted comes out clean.
For the cream prepare the custard following the instructions on the box/ sachet. In my case I needed 1 pint milk and 2 tbsp. sugar, made a paste then added the warm milk and gently boiled the mixture stirring all the time until it thickened.
Beat the butter and remaining sugar in a separate bowl. Add the cocoa powder. Mix with the cooled custard and fill the sponge.
Refrigerate for a few hours and then it's ready to serve!