On a floured surface roll the pastry to the thickness of a pound coin and line a 9 inch loose bottomed flan tin gently pushing the pastry into the corners and trimming off the excess.
Line the pastry with grease-proof paper and weight it down with dried beans or ceramic beans, cook for 15 mins then remove the beans and grease-proof and cook for a further 8 mins or until the pastry is pale golden.
In a pan of boiling water simmer the cauliflower for 5 mins until it starts to soften then drain and set aside.
In a frying pan cook the bacon until brown, remove with a slotted spoon and set aside. Turn the heat down and gently cook the onion in the same pan for 3-4 mins until soft.
Tip the cauliflower, bacon and onion into the pastry shell so they are fairly evenly distributed.
In a bowl combine the eggs, creme fraiche, chives and half the cheese and season to taste.
Pour the egg mixture into the pastry case and top with the remaining cheese. Cook in the oven for 30 minutes until the top is golden brown and it's cooked through with just a slight wobble in the center. Serve warm or cold.
NB. To make this a vegetarian option, miss out the bacon and add ½ tsp nutmeg to the egg mixture at the start of step 5.