For the short pastry, knead flour, 100 g sugar, salt, vanillin sugar, almonds, egg and butter in flakes with the dough hooks of the hand mixer. Knead again briefly with your hands, form into a roll and refrigerate for about 30 minutes.
Cut the dough roll into 6 slices. Place each slice in a well-greased tartlet mould (12 cm Ø) and press on. Prick several times with a fork and bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 14 minutes.
Take them out of the oven, let them cool down a little on a grid and turn out of the moulds. Let the shortcrust pastry tartlets cool down. Stir plum puree until smooth and spread into the tartlets. Wash, halve, stone and slice the plums.
Cover the tartlets with plums. Mix the cake glaze powder and the remaining sugar, gradually adding 125 ml of cold water and apple juice with a stirring spoon. Bring to the boil while stirring constantly.
Spread the glaze evenly over the cakelets and allow to set. Serve decorated with lemon balm as desired.