Leeks are a member of the onion and garlic family and in fact, they resemble giant green onions. They are milder in flavor than yellow or white onions and when cooked, have a delicate texture and taste
In a skillet, heat butter until melted. Add chopped leeks and thyme. Sauté on medium heat until leeks have softened, about 10 minutes (watch carefully because they can burn quite easily). Place in a bowl and let cool.
Roll out pie crust to fit a 9″ tart pan or pie plate. Crimp edges so it looks decorative. Use a fork to prick a few small holes in the bottom of the crust. Bake crust for 5 minutes. Remove from oven and set aside
In a large mixing bowl, combine eggs, cream, cheese, pancetta and cooled leek mixture. Stir until thoroughly combined. Season with fresh ground black pepper
Pour egg mixture into pie crust. Bake for 30 to 40 minutes, or until custard has set in the middle and the top is beginning to brown.