The very first thing that must be said about a proper quiche Lorraine is that it does not contain cheese. If it has cheese in it, it is still a quiche, but not one from Lorraine.
The only ingredients in a real quiche Lorraine are cream, eggs, bacon and salt and pepper as seasoning. The pastry should be a nice flaky shortcrust, which I think is best made with lard, plus some butter.
The other ingredients are streaky bacon cut into lardons and fried, I like smoked, but you can use unsmoked, 300 ml of double cream mixed with three beaten egg yolks and one whole beaten egg, plus pepper and salt (but be careful because the bacon will be salty).
Anyway, you make your pastry (according to your favourite recipe) and after letting it sit in the fridge for a couple of hours, you blind bake it in a flan ring with a removable base.
Then you add the filling and bake in the oven at 170C until it is set and the top is golden.
And that is it. A true classic.
And NO CHEESE!