Clean, wash and halve the Brussels sprouts if necessary. Cover and sauté in a little boiling salted water for 12-15 minutes. Drain well.
Grate the cheese. Whisk eggs and milk together. Season well with salt, pepper and nutmeg. Stir in the cheese.
Grease a tart pan with a removable base or a springform pan (26 cm). Place the puff pastry in the mold, press up 3 - 4 cm at the edge. Sprinkle the bottom evenly with breadcrumbs. Pour the Brussels sprouts into the mold and pour the egg milk over them. Sprinkle with pine nuts.
Bake in a preheated oven (top / bottom heat: 200 ° C, convection: 175 ° C, gas: level 3) for 40 - 45 minutes (cover with foil after approx. 30 minutes).