Measure out 100 ml orange juice and set aside. Stir 2 tbsp. orange juice with starch until smooth. Boil up the rest of the juice with cherries and 3 tbsp. sugar. Bind with the starch. Let the compote cool down.
Chopping chocolate. Mix quark, sour cream and 4 tablespoons of sugar. Stir in chocolate. Stir orange juice (100 ml) and rum.
Place the biscuits in a flat bowl close together and sprinkle with orange rum. Spread cherry compote and quark cream on the sponge cake and chill for at least 1 hour.