Grease a 10 inch springform pan and line with a baking paper. To prepare the curst, combine and sieve first five ingredients first in a bowl, cut in butter and egg until a smooth dough forms. Press firmly on the bottom and sides of prepare pan. Use a fork to prick the crust in regular intervals. Cover and chill the crust for 30 minutes.Pre-heat oven to 200C/400F. Stir chopped chocolate and sugar in a heatproof bowl set over a pan of simmering water until melted and smooth.
Remove bowl from over water and stir in the vanilla extract.
Let cool briefly until lukewarm but still pourable.Blend quark and cream cheese in another bowl until smooth.
Add in cocoa powder and 1 tbsp cornstarch. Stir to combine. Blend in eggs, one at a time. Gently stir in lukewarm chocolate until completely blended.
Pour filling over crust. Press cherries lightly into chocolate mixture if using.
Bake until the filling is set, about 50 minutes. Turn off the oven and let cool in oven with door ajar for about 1 hour. Take out and cool completely. Chill the cake overnight.In a pot, combine sugar and 1 tbsp cornstarch.
Add in cherry, lemon juice and stir until smooth. Cook over medium heat, stirring, until the mixture boils and thickens.
Remove from heat and let cool.
Drizzle the chocolate cheesecake with cherry sauce or simply just dust with icing sugar.
