Mix the flour with sugar in a bowl. Add the butter and egg and quickly knead everything with your hands to form a smooth shortcrust pastry. Wrap the dough in foil and cool for about 30 minutes.
Sort the blueberries, wash and pat dry. Roll out a third of the shortcrust pastry on a piece of baking paper into a circle (Ø 26 cm) and put in a cool place. Grease a springform pan (26 cm Ø) and dust with flour.
Preheat the oven to 180 degrees. Roll out the remaining shortcrust pastry thinly on a floured work surface and line the prepared springform pan with it, forming an edge about 4 cm high. Prick several times with a fork. Mix the berries with sugar and cornstarch and distribute evenly on the dough.
Cut 8-10 strips from the cool shortcrust pastry circle and place them on the tart as a grid. Lightly press the strips on the edge of the tart. Bake the cake in the preheated oven for about 60 minutes, possibly after 30 minutes cover with aluminum foil. Take out and let cool down. Bring the jam to the boil in a saucepan while stirring and brush the cold cake with it. Divide the cake into pieces and serve with 1 scoop of vanilla ice cream.