Puree 2/3 of the strawberries in a blender with vanilla sugar, sugar and lemon juice. Leave the remaining strawberries to decorate.
Make a cream from mascarpone, quark, whipped cream, a little lemon juice and powdered sugar, if you like. Mix 2/3 of the mixture of the pureed strawberries with the mascarpone cream.
Line a rectangular shape with a layer of ladyfingers. Drizzle with strawberry liqueur or orange juice. Spread half of the mascarpone cream on the ladyfingers. Place a layer of ladyfingers on top and drizzle with liqueur or orange juice. Spread the rest of the mascarpone cream on top and spread the rest of the strawberry puree over it. Decorate with the strawberries and mint leaves that were left behind.