Mix 200 g flour, 100 g fat, 1/2 teaspoon salt, egg and 2 tablespoons water with the dough hooks of the hand mixer. Then work into a smooth dough with cool hands.
Covered and let it rest in the refrigerator for about 1 hour. Meanwhile clean and wash the Brussels sprouts and cook in boiling water for 6-8 minutes. Drain well on a sieve. Cut the smoked pork loin into cubes. Heat the rest of the fat in a pot, dust with the rest of the flour and sauté.
Add milk while stirring and bring to the boil. Season with salt, pepper and nutmeg. Add Brussels sprouts and pork loin and cook at low heat for about 3 minutes. Meanwhile grate cheese finely. Add 100 g to the sauce and let it melt.
Roll out the dough on a lightly floured work surface until round (approx. 33 cm Ø). Grease a flat quiche tin (approx. 29 cm Ø) and line with the dough. Sprinkle with breadcrumbs. Spread the Brussels sprouts and casserole ragout on the dough and bake in a preheated oven (electric range: 175 °C/ gas: level 2) for 50-60 minutes.
20 minutes before the end of the baking time, sprinkle the remaining cheese on top and bake.