Cut the fat into cubes. Knead flour, sugar, fat, egg yolk and approx. 2 tablespoons of ice water to a smooth short pastry. Cover and put in a cool place for about 30 minutes. Grease the moulds and sprinkle with breadcrumbs.
Roll out the short pastry on a floured work surface. Cut out 8 circles (approx. 10 cm Ø) and press them into the moulds. Prick several times with a fork and bake in a preheated oven (electric cooker: 200°C/ gas: level 3) for about 15 minutes.
Turn out of the moulds when hot and let it cool down on a cake rack. Clean, wash and slice the rhubarb diagonally. Bring 1/4 litre water, 50 g sugar and vanillin sugar to the boil. Steam rhubarb for 3-5 minutes.
Drain, collect the liquid and let it cool down. Sort the raspberries. For the cream, stir egg yolks and remaining sugar until creamy. Stir in mascarpone, lemon peel and lemon juice. Spread into the tartlets.
Cover with rhubarb and raspberries. Mix the cake glaze and cold rhubarb stock in a pot. Bring to the boil while stirring. Spread over the fruit and refrigerate for a short time. Makes about 8 tartlets.