For the layers:
Beat the egg whites into snow. Add the sugar gradually and continue to mix until thickened. Add the walnuts. Mix everything well and then divide the mixture into 4 parts, bake them separately in a large baking dish, with baking paper on the bottom that you've coated with butter and sprinkled with flour. Bake in a moderate oven.
For the cream:
Boil the sugar to a thick syrup with 1/2 cupful of water and the chocolate, while stirring constantly to avoid lumps. While still warm, add the egg yolks to the syrup. Mix everything well and leave to cool. Beat the butter very well and add a bit of the cold mixture to it. Make a fluffy cream.
For the caramelized sugar:
Mix the sugar with 2 tablespoons of water to caramelize and pour it into a greased baking dish. Once cool, crush it finely.
Stick the cake layers together with the cream and sprinkle some of the caramelized sugar over it. Top with cream and decorate as desired - with coconut, green or chocolate sprinkles. You can make this cake without the caramelized sugar as well.