Mix flour, 3 tablespoons of sugar, 1 packet of vanillin sugar and salt in a bowl. Add the egg yolks and butter in small pieces and knead first with the dough hook of the hand mixer, then with your hands to a smooth dough.
Wrap in foil and chill for about 30 minutes. Grease 6 tartlet cups with lift-off base (approx. 12 cm Ø) and dust with flour. Roll out the dough thinly on a lightly floured work surface and cut out 4 circles (each approx. 16 cm Ø).
Line 4 moulds with it, press the rim well. Cut off any excess dough. Prick the cake several times with a fork. Knead the remaining dough again and roll out. Cut out 2 more circles, place them in the remaining moulds and prick them as well.
Cut the baking paper to the size of the ramekins. Place in the moulds and add dried peas. Bake in the preheated oven (electric range: 225 °C/ convection oven: 200 °C/ gas: level 4) for approx. 15 minutes until they are blind.
Clean, wash and cut the rhubarb into small pieces. Boil up the raspberry syrup. Cover the rhubarb pieces and steam for 3-4 minutes. Stir occasionally. Mix starch with some water. Bind the syrup with it, pour into a bowl and let it cool down.
Remove baking paper and dry peas. Bake the Tartelettes at the same temperature for about 5 minutes. Remove and let cool off. Mix mascarpone, 3 tablespoons of sugar, 1 packet of vanillin sugar and sour cream.
Remove the Tarteletts from the moulds. Pour the mascarpone cream into the moulds. Add the rhubarb compote.