Clean and wash the Brussels sprouts and cook in boiling salted water for 15-20 minutes. Knead flour, 1/2 tsp salt, hazelnuts, butter and 1 egg to a smooth dough. Wrap in foil and chill for about 30 minutes.
Heat the oil in a coated pan. Fry the minced meat for 3-4 minutes until crumbly, season with salt and pepper. Clean, wash and cut the peppers into pieces. Drain the Brussels sprouts and rinse in cold water.
Stir milk and 3 eggs until smooth. Season to taste with salt and pepper. Roll out the dough on a floured work surface and line a greased, floured tart tin (26 cm Ø) with lift-off base.
Sprinkle the bottom with breadcrumbs. Grate cheese. Layer minced meat, Brussels sprouts and paprika in the mould. Pour over egg milk, sprinkle with cheese and bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: stage 2) for 35-45 minutes until golden brown and the egg milk has set.