Wash the mint, put 4 small stems aside for decoration. Pluck off remaining leaves and crush them with 1-2 tbsp. sugar in a mortar. Wash the lime, dab dry and grate the peel. Halve the lime and squeeze it.
Mix quark with sour cream, vanilla sugar, lime juice and lime zest until smooth. Season the mixture with 2-3 tablespoons of sugar.
Pour the lime cream, up to about 4 teaspoons, into small glasses. Place 4 orange cookies on each and sprinkle with mint sugar. Spill the rest of the cream on top and decorate with the remaining biscuits and mint.