Drain and slice the mozzarella. Wash and separate the broccoli florets. Cook them for 5 minutes in a saucepan of boiling salted water (or steam). Drain them
Peel and slice the onion, brown it 5 minutes in an oiled frying pan, stirring. Add the bouquets of broccoli and bacon, stir 3 minutes. Salt little, pepper
Spread the puff pastry, fill an oiled pie tin (round or rectangular). Cover it with mozzarella cheese and add the broccoli pan.
Put the pie in the oven and bake it for 15 minutes. Cover the filling with baking paper and bake again 15 minutes. Serve as soon as out of the oven