- 50-73 g margarine or butter, soft
- 50 g brown sugar
- 1 egg yolk
- 2 tbsp dark cocoa
- 1 tsp vanilla sugar or vanilla extract
- Cream together the eggs and sugar.
- Add the flour and potato starch, little by little.
- Prepare a temporary baking container by putting baking paper on a baking sheet and folding in the corners to make a shallow "box".
- Pour in the dough and smooth with a spatula.
- Bake at 250 °C for about 10 minutes.
- Set the oven to heat from below.
- Test for doneness by gently pressing the top of the cake with your finger - if the cake feels firm and the fingerprint quickly disappears, the cake is done.
- When done, turn the cake over onto a sheet of baking paper sprinkled with sugar.
- Put a roasting pan or cutting board on top of the cake while it cools, to keep it smooth and prevent it from hardening.
- Cream together margarine and brown sugar.
- Add the egg yolk and mix well.
- Add the flavouring and sifted cocoa.
- When the cake is cold, smooth the butter cream over one side of it and firmly but carefully roll up the cake.
- Slice and serve with a dollop of whipped cream.
Instead of chocolate buttercream, you can use white butter icing with the flavouring of your choice, chocolate pudding or jam. Strawberry or raspberry jam tastes especially good with this kind of cake.