To make the pastry, cut the butter into cubes, sift the flour into a large bowl, and use your fingertips to rub the flour and butter together until the mixture resembles breadcrumbs.
Add the water and knead gently into a dough.
Cover the dough with clingfilm, and refrigerate for at least 30 minutes.
When the pastry is chilled, use a rolling pin to roll it, arrange it over a quiche/flan tin, and use a fork to prick it in a few places.
Cover the tin with non-stick paper, and fill it with dry pulses or baking beans.
Bake in the preheated oven at 220 degrees Celsius (430 Fahrenheit) for 10 minutes, then remove the paper and dry pulses, and bake again for a further 10 minutes until golden.
To make the filling, peel and chop the onion.
Heat up the oil on a low heat, add the onion with a pinch of salt, and fry until golden.
Add the onion to the pastry, scattering it well over the bottom of the pasty.
Add the cooked bacon chopped into pieces and the grated cheese.
In a jug, beat the eggs, add the cream, and mix well.
Pour the mixture over the pastry.
Decrease the oven temperature to 180 degrees Celsius (350 Fahrenheit).
Bake for 25 minutes until the quiche is golden and set.