For the Philadelphia Chocolate Mint Cake, place biscuits in a freezer bag, seal bag and crumble contents completely with a rolling pin or your hands. Melt the butter and Milka chocolate, mix with the crumbs and press into a springform pan lined with baking paper. Mix Philadelphia, yogurt and mint syrup with electric hand mixer.
Briefly soak gelatine in cold water and squeeze out. Heat with 150 ml water and sugar until gelatin is dissolved. Stir briskly into the Philadelphia cream. Pour the cream into the springform pan. Refrigerate the cake for at least 3 hours. Before serving, decorate the Philadelphia chocolate mint cake with chocolate hearts.