Quiche Lorraine is one of the quintessential quiches. The combination of leek and bacon is perfect. I have seen versions with onion or green onion, but the buttery sweetness of leek, I think, is unbeatable in conversation with egg, bacon, and Gruyere. Gruyere is the best cheese to use, but a freshly grated Swiss cheese will make a beautiful pastry as well. For this meal, I poured my filling into tart crusts instead of pie crusts to create a different filling to crust ration and we all loved it!