Sieve the flour and salt into a bowl and rub in the butter.
Add the egg and water to form a dough ball, then chill for one hour.
Roll out the pastry, line a 25cm greased flan case, and chill for 30 minutes.
Preheat the oven to 180°C.
Bake the pastry blind with paper and beans for 20 minutes.
Trim excess pastry after resting the case.
Fry the bacon in oil until browned, then remove using a slotted spoon.
Sauté the onion in butter and the remaining oil until colored.
Spread cooled onions, bacon, and soft cheese into the pastry case.
Whisk eggs, cream, 110g of hard cheese, and parsley together.
Season the mixture and pour it into the tart case to bake for 20 minutes.
Add the remaining cheese and nutmeg and bake for 10 minutes until set.
Cool for five minutes before removing the ring and serving.