Break the chocolate into pieces and melt in a hot water bath at low heat. Let it cool down a little. Soak gelatine in cold water for about 5 minutes. Grind 80 g pistachios finely in the universal chopper.
Whip 500 g cream until stiff. Mix 2 tbsp. whipped cream, ground pistachios and vanilla sugar with the liquid chocolate.
Squeeze the gelatine and dissolve it carefully in a small pot at very low heat while stirring. Stir 2 tablespoons of pistachio chocolate into the gelatine, then stir everything into the rest of the chocolate mixture.
Stir in yoghurt and fold in the remaining whipped cream. If necessary, fill the cream into eight to ten glasses (each containing approx. 1⁄4 l) using a piping bag. Chill for at least 2 hours.
Finely chop 20 g pistachios and whip 200 g cream until stiff, adding liqueur at the end. Pour cream into a piping bag with a large star-shaped spout. Spray tuffs onto the cream and sprinkle with pistachios.
Garnish with chocolate strawberries if desired. Keep cool until serving.