To make the pastry, process the flour and butter until it resembles fine breadcrumbs.
Slowly add the water while processing, until the mixture comes together into a ball.
Roll out with a rolling pin and lay into a tray, prick the bottom with a fork and refrigerate for 30 minutes.
Bake for 20 minutes on medium heat or until golden.
To make the filling, heat the oil in a frying pan, and add the finely chopped onion and diced pancetta and cook until crispy and caramalised. Leave to cool.
Whisk the eggs and cream and add to the cooled onion/pancetta mixture.
Pour the mixture into the pastry shell and top with grated cheese and bake for 30 minutes or until golden brown and set.