Ingredients: For the sponge: 1 tsp instant coffee, 4 large eggs, 85 g sugar, 120 g flour (or gluten free flour + 1 tsp xanthan gum), 2 tbsp cocoa powder.
For the icing: 50 g dark chocolate, 250 g mascarpone, 50 g sugar, 2 tbsp cocoa powder, 1 tsp instant coffee, a few blueberries to decorate.
Preheat the oven at 180 C.
Mix the coffee with 1 tbsp warm water. Beat the eggs, sugar and coffee mix into a large bowl until the mixture is thick and airy.
Sift in the flour and the cocoa powder and fold it in gently with a spatula.
Pour the mix onto a large tray, and level it properly. Bake for 12-15 min or until the cake feels spongy but firm when touched.
Lay a sheet of baking paper on a working surface and sprinkle with sugar. Tip the tin upside down and let the cake fall out. Remove the paper used for baking.
Roll out the cake lengthways, rolling it with the paper so it doesn't stick. Let it cool down.
Melt the chocolate.
Mix the mascarpone with the cocoa and sugar.
Add the chocolate and instant coffee.
Unroll the log, fill it with cream (save some for the top) and then roll the log back.
Pour some of the cream on top.
