For the mousse, heat the cream in a saucepan. Break the chocolate into pieces and melt in the cream. Pour into a large mixing bowl and cover directly on the surface with cling film. Let it cool down a little, then put it in a cool place for about 5 hours.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a springform pan (26 cm Ø) and dust with flour. For the base mix 125 g butter, 125 g sugar, vanilla sugar and 1 pinch of salt for about 8 minutes with the whisks of the mixer until creamy.
Stir in the eggs one by one. Then mix 125 g buckwheat flour, breadcrumbs, ground nuts and baking powder and stir in 2 portions briefly.
Cut bread into cubes. Heat 4 tablespoons of oil in a frying pan and fry the bread cubes while turning them into croutons. Season with salt and pepper. ##Peel garlic and onion and cut into fine cubes.
Approx. 1⁄4 of the nut kernels in half. Remove the base from the mould and place on a plate. Carefully remove the foil from the chocolate cream. Whip the chocolate cream with the whisks of the mixer until it is thick and creamy.
Spread loosely on the floor. Chill for about 1 hour.
Mix cocoa and 1 teaspoon sugar. Sprinkle the cake with the mixture before serving, halve and spread whole nuts on top.