Mix the quark, milk and 3 tablespoons of the mandarin juice. Season to taste with sugar, vanilla sugar and rum. Fold in the cream. Roughly chop the chocolate and stir into the quark, except for something to sprinkle. Fold the mandarins into the quark, except for a few to decorate. Divide into four dessert bowls. Sprinkle with the rest of the chocolate. Spread the mandarins and orange fillets on top. Garnish with lemon balm.