Separate the whites from the yolks and whip them.
Mince finely the hazelnuts.
Mix the yolks with the butter and the sugar. Add the whipped whites, all-purpose flour, cocoa and hazelnuts.
Dissolve the baking powder in the milk and add to the mixture.
Pour in a buttered baking pan and bake in preheated 180° C (356 F) oven 40 minutes.
Sprinkle with icing sugar before serving.
Hazelnut Cake
250g hazelnuts, toasted
3 eggs
50g butter
175g sugar
90g bitter cocoa
150g all-purpose flour
1 tsp. baking powder
2 tbsp. milk
icing sugar