Finely chop the walnuts, except for 12 pieces to decorate.
Preheat the oven to 175 ° C top / bottom heat. Grease a springform pan with a diameter of 26 cm and sprinkle with flour.
Using the electric mixer, whip the sugar, vanilla sugar, salt and butter until creamy white. Mix in the eggs one by one. Mix the flour, baking powder, grated chocolate and chopped walnuts and stir into the egg cream. Add the amaretto and stir in. Put the dough in the springform pan and smooth it out a little.
Put the cake in the oven and bake for about 45 minutes, make a stick test, remove it and let it cool in the tin for 10 minutes. Remove from the tin and place on a wire rack.
For the topping: bring the brown sugar, butter and cream to the boil. Simmer for approx. 3 minutes until an even mixture has formed. Spread the icing on the cake and decorate with the remaining walnuts. Then cut the cake into 12 pieces with a knife coated with oil.