Some things need a little sugar. We often add a bit to a tomato sauce we throw together. It seems to temper the acidity of the tomatoes. We also add a bit of sugar to a chicken liver and mushroom pâté that wins rave reviews. Again, it seems to mitigate a certain harshness that can be present in the chicken livers and gives the pâté a rounder or fuller flavor.
With regard to your Baked Three-Cheese Egg Casserole, we would also be tempted to leave the sugar out. The recipe, with loads of eggs, heaps of cheese, and a certain amount of butter, looks rich, even to us, but we’re not sure sweetness will do anything to cut the richness. The sugar is not in the recipe to cause a magical chemical reaction or produce some unexpected lightness. It is meant to tweak the flavor, and we’re not sure it’s heading in the right direction.
When the real world confronts us and we don’t have time to make a quiche crust, we occasionally turn to a ready-made pie crust from the grocery store. You have to be careful, though, that you are not buying a sweetened crust meant for a dessert pie. Some stores only have sweet crusts. They are not very sweet, but they do nothing good to a savory quiche. Just that hint of sweetness turns a quiche made with great ingredients into a disappointment.
Not every recipe is a winner, you know, nor is every recipe set in stone. We’d leave out the sugar. If the casserole is disappointing and you try it again, we would add some cooked spinach or mushrooms to make it more interesting. For that matter, we wouldn’t even make it the first time without a bit of cooked onion, which will add a little sweetness, but also a serious boost in flavor. Add a small amount of garlic, if your tastes lead in that direction, or a pinch of an herb or spice that you particularly like. You can certainly dress it up in a way that suits your cooking style and taste buds.