For the short pastry, quickly knead flour, butter in flakes, sugar, hazelnuts and 1 tbsp. water with your hands to a smooth dough. Roll out approx. 2/3 of the dough on a floured work surface until round (approx. 30 cm).
Pour the dough into a greased tart mould (26 cm Ø) with lift-off base and press it down. Cut off protruding edges. Prick the base several times with a fork. Chill for about 30 minutes. Knead the rest of the dough with the remaining 1/3 of the dough, wrap in foil and also refrigerate.
Stir jam and starch until smooth. Select the blueberries, wash and drain well. Mix jam and blueberries and distribute in the mould. Roll out the remaining dough on a floured work surface until round (approx. 27 cm Ø) and thin.
Cut out a few stars. Place the dough on the tart, press on the edge and cut off any excess dough. Spread the stars on the dough. On the lower rail in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see
manufacturer) bake for about 35 minutes. Let it cool down on a cake rack. Remove from the tin and dust with icing sugar.