For the dough, warm milk lukewarm. Rinse lemon hot, dab dry and finely grate half the peel. Mix with 350 g flour, yeast, sugar and 1 pinch of salt. Add eggs. Add warm milk. Stir in with the dough hooks of the mixer, kneading 60 g soft butter in flakes.
When the dough separates from the bowl rim, continue kneading for about 2 minutes. Cover the dough and let it rise in a warm place for about 30 minutes.
For the filling, select the blueberries, wash and drain if necessary. Mix with berry jam. Grease a pieform (26 cm Ø). Knead the dough on some flour and roll out to a rectangle (approx. 30 x 45 cm).
Spread the jam berries on top, leaving about 2 cm of edge free all around. Roll up the dough from the long side and cut into 10-12 slices. Place the dough snails upright next to each other in the mould and let them rise covered for about 1 hour.
Preheat oven (electric cooker: 175°C/circulating air: 150°C/gas: see manufacturer). Bake in hot oven for approx. 25 minutes. Squeeze lemon. Mix approx. 2 tsp. juice with icing sugar to a smooth glaze.
Take the cakes out of the oven. Leave to cool for about 30 minutes. Drizzle the casting over it. Let it cool down.