For the compote, drain the plums and collect the juice. Stir 2 tablespoons of juice with starch until smooth. Boil up the rest of the juice with cinnamon stick, lemon peel and sugar. Stir in the starch and simmer for 5 minutes at low heat. Add plums and let it get cold. Remove cinnamon stick and lemon peel. Soak gelatine in cold water.
Beat egg yolks, marzipan and lemon juice until creamy. Squeeze the gelatine and dissolve at low heat. Stir the mascarpone and gelatine into the cream and let it absorb a little. Beat the egg whites until very stiff and fold into the cream. Spread the compote over two dessert glasses and let it set in the fridge. Decorate with mint leaves as desired