Mix 200 g pistachios and 50 g icing sugar very finely in the universal chopper. Beat the egg whites until stiff, while pouring in 100 g icing sugar. Fold in the ground pistachios and fill into a piping bag with a medium sized nozzle
Draw two circles (approx. 18 cm Ø each) on a piece of baking paper. Spray the mixture spirally from the centre onto the circles. Bake on the lower shelf in a preheated oven (electric range: 150 °C/ convection oven: 125 °C/ gas: see manufacturer) for 15-20 minutes. Coarsely chop 50 g pistachios. Roast the flaked almonds in a pan without fat. Take out and let cool down. Remove the cake base from the oven and let it cool down on a cake rack
Roughly chop the chocolate. Heat the cream. Melt the chopped chocolate in the cream, stirring occasionally. Add butter and mix well. Cover with cling film so that the film lies directly on the cream and chill for at least 1 hour.
Whip the chocolate cream with the whisks of the hand mixer for 30-60 seconds (may only become slightly firmer) and fill into a piping bag with a perforated spout. Spray cream in thick tuffs on one base, then place the second base on top. Refrigerate the cake for about 30 minutes, then sprinkle with icing sugar, flaked almonds and the rest of the pistachios
waiting time approx. 2 hours