For the shortcrust pastry
Wash and dry the basil. Blend it in a food processor with 50g of butter and 50g of flour taken from the total amounts. When the mixture is smooth, combine it with the rest of the flour and butter. Add a pinch of salt and knead quickly with your fingertips. Add a drizzle of water and make a ball. Cover with film and let rest in the refrigerator for at least 30 minutes.
Clean the leeks, cut into slices, and cook them in a frying pan with a little oil over a low flame (add a ladle of water or broth occasionally so they won’t burn), Add salt and pepper to taste. In a frying pan, brown the bacon. Let it cool. Beat the eggs in a bowl and add the cream, Parmigiano, leeks and bacon, salt and pepper.
Butter and flour an oven dish. Roll out the shortcrust pastry to a thickness of 3-4 mm to cover the dish. Prick the pastry on the bottom with a fork, cover with baking paper and spread some beans to with it down, pressing slightly so it takes shape.
Bake at 180° for 20 minutes. Remove from the over and remove the paper with the beans. Pour in the mixture of eggs and leeks. Bake for another 20 minutes or until golden brown on the surface. Remove from oven, slice and serve.