Roll out the dough on a lightly floured surface and line the flan tin / dish, pressing into the fluted edges; leave the edges overhanging the sides. Place in the fridge to chill for 30 mins.
Preheat the oven to 200c / 400f. Prick the pastry case all over with a fork, to prevent air bubbles forming during baking. Line the base and sides with baking parchment and weigh it down with baking beans or rice, making sure it is filled right the way up the sides of the pastry base to prevent the sides from collapsing in. Place on a baking sheet and bake for 10 minutes, this is baking blind.
Separate an egg for an egg wash using the egg white, reserve the egg yolk. Remove the beans and paper from the pastry base, paint lightly beaten egg white onto the pastry base and bake the empty case for a further 10 minutes, or until the pastry is lightly browned. This is to seal the pastry base and prevent a soggy bottom.
Once baked remove the pastry case from the oven and leave to cool. Using a sharp knife, trim the overhanging pastry.
Reduce the oven temperature to 180c / 350f.
Now to make the filling. Crisp the bacon in a sauté pan over a medium heat for 10 minutes. Transfer to the cooled pastry case with a slotted spoon. Leave the juices in the pan.
Place the chopped onion in the pan and cook over a medium heat for 8 minutes until golden. Add to the pastry case and top with the grated cheese.
In a bowl, combine the eggs (including the reserved yolk and any left over egg white from the egg wash), milk, herbs, salt and pepper, then pour into the flan.
Place on a baking sheet and bake for 25-30 mins until golden and just set. Be careful not to overcook the quiche or the filling will become tough.
Enjoy!

