Chop the chocolate and melt with butter over a warm water bath. Stir in almond slivers and spread as a base in a square springform pan (24 x 24 cm). Chill for about 15 minutes.
Soak gelatine in cold water. Stir the quark, 100 g sugar, vanillin sugar and lemon juice until smooth. Squeeze out the gelatine, dissolve, mix with 2 tbsp. cream and stir into the remaining cream. Whip the cream with the whisks of the hand mixer until stiff and fold into the cream. Spread the quark cream on the base and refrigerate for about 10 minutes. Using a teaspoon, make grooves in the cream and chill for approx. 2 hours
Cut the passion fruit in half and scrape out the flesh. Bring 200 ml juice and 50 g sugar to the boil. Mix 5 tbsp. juice and starch, bind juice with it, bring to the boil again. Stir the passion fruit flesh into the thickened juice and let it cool down for about 5 minutes. Carefully spread the passion fruit sauce into the grooves on the cake. Chill the cake for another 15 minutes.
waiting time approx. 2 3/4 hours