Beat 4 egg whites until stiff, adding 175 g sugar. Carefully fold in ground almonds and hazelnuts
Pour the mixture into a piping bag with a medium-sized punched spout and squirt two circles of equal size (approx. 21 cm) onto a baking tray lined with baking paper. Bake circles in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 15-20 minutes. Take out and let cool down
In the meantime, chop the hazelnuts and roast them in a pan without fat. In a saucepan, caramelise 125 g sugar with 3 tbsp water until golden. Add the nuts and mix with the caramel for about 1 minute. Put the caramel on baking paper and let it cool down. Finely chop the nuts or mix them in a universal chopper
Boil down 100 g sugar and 4 tablespoons water in a pot for about 5 minutes to a syrup. Beat 2 egg whites until stiff, while pouring in 1 tablespoon of sugar. Add the syrup at the end while stirring
Beat the butter and 50 g caramelised nuts until light and creamy with the whisk of the hand mixer. Add the egg whites while stirring to create a mousse-like cream. Place a cake ring around a base. Pour the cream onto the base and sprinkle the rest of the nuts, except for 1 tbsp.
Place the second base on top and chill for at least 2 hours. Just before serving, dust the cake with icing sugar and decorate with the remaining chopped nuts
waiting time approx. 2 1/4 hours