Wash lemons thoroughly and rub dry. Grate the peel of one lemon and squeeze the juice. Cut remaining lemon into thin slices. Mix quark, lemon peel, lemon juice, vanillin sugar and sugar. Whip cream until stiff and fold into the lemon quark mixture. Line plates with lemon slices, spread lemon cream on top and serve decorated as desired with lemon julienne and lemon balm