Drain the morello cherries thoroughly, then add kirsch and let steep for 10 minutes.
While the cherries steep, mix the quark, milk, sugar, and vanilla sugar together with a whisk.
Whip the cream until stiff peaks form (about 2-3 minutes with an electric mixer, longer by hand).
Fold the whipped cream loosely into the quark mixture.
Layer the cherries and quark mixture into dessert glasses by alternating between them, starting with cherries and ending with quark on top. Garnish each glass with morello cherries and chocolate flakes.