For the dough, grease a tart mould with a lifting base (26 cm Ø; 4 cm high). Knead 250 g flour, 75 g sugar, 125 g butter in pieces and 1 egg first with the dough hooks of the mixer, then quickly with your hands to a smooth dough.
Roll out the dough on a floured work surface until round (approx. 30 cm Ø). Line the mould with it and press the dough on the edge. Chill for about 30 minutes.
Meanwhile, wash and sort the blueberries for the filling and let them drain well. Mix blueberries and jam.
For the icing, whisk 5 eggs, crème fraîche, 125 g sugar and vanilla sugar with a whisk until smooth.
Sprinkle the dough base evenly with breadcrumbs. Spread blueberries on top. Carefully pour the icing over it.
Bake in the preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: see manufacturer) on the lowest rack for 30-35 minutes. Let the tart cool down. Then remove from the mould. Serve with crème fraîche and walnut ice cream.