Preheat the oven to approx. 170 degrees hot air. (Please choose the temperature according to your own oven)
Protein mass:
Beat the egg whites with a squirt of lemon juice until stiff enough that a knife cut is visible. Gradually pour in the sugar while stirring, then carefully fold in the amaretto and finally the ground walnuts and the grated chocolate.
Batter:
Mix the room temperature butter in a mixing bowl with a hand mixer (whisk) or food processor until foamy. Gradually add sugar and vanilla sugar while stirring, until a thickened mass is formed. Stir in each egg and yolks for about ½ minute at the highest level. Mix flour with baking powder and cornstarch, sieve and stir in briefly.
Pour a quarter of the batter into the greased and floured Gugelhupf tin and make a slight indentation in the middle. Put half of the egg white mixture on the dough, smooth out. Spread almost half of the remaining dough on top, also make a depression, pour in the remaining egg white mixture, smooth it out and cover evenly with the remaining dough.
Bake for about 60 minutes at 170 - 175 degrees hot air.
After baking, let the cake rest in the tin for 10 minutes, then turn it out onto a wire rack and let it cool down.
Sieve 2 tablespoons of powdered sugar, mix with 1 teaspoon of lemon juice to form a viscous glaze. Spread it on the underside of the walnut halves and glue it to the cake.