Clean and wash the Brussels sprouts and halve them according to size. Cook in boiling salted water for about 10 minutes. Place the puff pastry slices next to each other and defrost. Whisk cheese, eggs and milk.
Season with salt, pepper and nutmeg. Place the puff pastry slices on top of each other and roll out into a circle (approx. 26 cm Ø). Grease a tart tin (22 cm Ø) and line with the dough. Quench the Brussels sprouts in ice water, drain in a sieve and distribute in the tin.
Pour egg milk over it. Brush the edge of the puff pastry with some egg milk. Spread pine nuts over the tart. Bake the tart in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 40 minutes.