Preheat the oven to 200 ° C (convection). Line a greased springform pan (28 cm) with the puff pastry.
Dice the bacon and onions. Lightly fry the bacon in a hot pan without fat, add the onion cubes and fry briefly. Put both in the springform pan and spread a little on the dough.
Mix the eggs with cheese and crème fraîche in a bowl and season well with pepper and nutmeg, only add a little salt. Pour the mixture over the bacon and onions.