For the cake, grease a square (24 x 24 cm) or round springform pan (26 cm Ø) and sprinkle with sugar. Coarsely chop the hazelnut kernels.
Break chocolate into pieces. Melt with butter in a hot water bath. Leave to cool at lukewarm. Separate the eggs. Beat the egg whites until stiff, chill them. Cream egg yolk and 250 g sugar with the whisks of the mixer.
Stir in ground nuts and liquid chocolate mass briefly. First fold in chopped nuts and then beaten egg white. Brush into the mould. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 45-55 minutes.
Leave to cool in the mould for about 20 minutes. Remove and let cool completely.
For the salad, wash, clean and slice the strawberries. Sprinkle with 2 tablespoons of sugar and let the juice stand.
Mix the crème fraîche and vanilla sugar. Whip the cream until stiff, fold in and cut the cake into approx. 20 cube-shaped pieces. Serve with strawberry salad and vanilla cream.