Let the raspberries thaw in a sieve. Put the yoghurt with egg liqueur in a bowl and stir until smooth with a whisk. Season to taste with lemon juice and vanilla sugar.
Place 150 g raspberries in a tall mixing bowl and puree finely with a hand blender. Mix 250 g raspberries with jam sugar and also puree finely. Leave to stand for about 10 minutes. Stir in the remaining puree. Leave to stand for another 5 minutes. Stir in 100 ml apple juice.
Wash the lemon balm, shake dry and pluck the leaves from the stalk. Divide 3/4 of the puree into 4 glasses. Carefully pour 1/4 yoghurt-egg liqueur mixture onto each glass. Marble lightly with a wooden skewer. Carefully pour the rest of the raspberry puree onto the yoghurt with a teaspoon. Decorate with lemon balm.