Melt butter in a small pot. Put the cinnamon stars in a freezer bag (3 litres capacity) and crumble them with a kitchen roll. Put cinnamon star crumbs and butter in a bowl and mix well with a fork. Lightly oil the bottom of a springform pan (26 cm Ø). Spread the crumbs on it and press them down firmly with the back of your hand. Put the base in a cool place for about 1 1/2 hours.
Soak gelatine in cold water. Pour mandarin oranges into a sieve and drain well, collecting the juice. Mix yoghurt, quark, mascarpone, vanilla sugar, sugar and 6 tablespoons of mandarin juice with the whisk of the hand mixer. Whip the cream until stiff. Squeeze the gelatine well and melt in a small pot at low heat. Remove from the heat and stir in 3-4 tablespoons of the quark mixture drop by drop. Slowly run into the remaining cream and stir in well. Carefully mix in mandarin oranges. Set aside for 3-4 minutes until the cream begins to gel. Fold in cream in portions. Pour the cream onto the base, spreading the surface in waves. Chill the cake for 4 hours.
Slowly run into the remaining cream and stir in well. Carefully mix in mandarin oranges. Set aside for 3-4 minutes until the cream begins to gel. Fold in cream in portions. Pour the cream onto the base, spreading the surface in waves. Chill the cake for 4 hours. Then remove from the edge of the springform pan with a knife. Place the cake on a cake plate and decorate with cinnamon stars and dust with cinnamon and icing sugar as desired.
waiting time approx. 5 1/2 hours