This is a slow-cooking weekend recipe, that is well worth the time. Leeks, shallots, yellow onions and green onions are slow-cooked to bring out their sweetness, then baked as a delicious tart with creme fraische and fresh thyme. I use store-bought crust for this recipe, but if you have the time feel free to use your favourite short crust recipe if you prefer to make everything from scratch. 8-10 pieces depending on serving size.