For decorating, set 6 Nippons aside. Break remaining into small pieces and melt in a bowl over a pot of hot (not boiling) water. Brush a pie plate lightly with soft butter and put a springform pan rim around. Stir Nippon mixture, pour into pie plate, smooth and set for about 1 hour in the refrigerator.
Drain cherries in a sieve and collect the juice. Mix cornstarch with some juice until smooth. Boil 150 ml (approximately 5 ounce) juice, stir in cornstarch, boil and allow to thicken. Pull from heat, let cool and pour in cherries.
Beat cream with cream stabilizer, vanilla and sugar until stiff. Mix 2/3 of the cream into mascarpone. Spread 1/3 of the mascarpone cream evenly on the Nippon mixture, distribute cherry mixture on top, then spread remainder of the mascarpone cream. Decorate cake surface with a cake decorating comb.
Place remaining cream into a piping bag with a large tip, pipe 12 cream rosettes on the cake and then place in the refrigerator for about 2 hours. Cut remaining Nippon in half diagonally and press one of each in the cream rosettes. Cut and serve.