Beat together very well six large eggs and 2 cups of heavy cream; you can use half-and-half in a pinch, but even whole milk, won’t give you the best meld. Season with salt and pepper; nutmeg is traditional, but I never seem to have any on hand.
Pour half of this mixture into an 8-in. crust, add mushrooms and spinach–about a half cup of each–and a sprinkling of grated cheese, then pour on the rest of the egg mixture. Shake the pan to settle.
Top with a little more cheese for dining room drama and bake at 375 for about 30 minutes or until the top is puffed and slightly browned. Cool on a counter rack and brush with melted butter before slicing and serving.