I use that concept and make savory custards out of just about anything! This is a meal we especially love during the spring when the chickens and ducks start laying well. For more main dish egg ideas, check out my book Design a Dish.
4tablespoonsbutteror combo of butter and coconut oil
Cook onion in oil until soft.
Combine cooked onion, veggies, eggs, salt, pepper and nutmeg.
Put mixture into well buttered casserole dish, baking pan, or cast iron skillet.
Bake at 350 for 30 to 40 minutes until eggs are solid.
*Veggie Notes:You can make this savory casserole out of just about any vegetable as long as it isn't too wet. I like to use this recipe to use up leftovers that are lurking in the fridge. The following vegetables are best pureed or mashed; acorn squash, butternut squash, sweet potato, spaghetti squash (I don't puree this one), and carrots. Chopped and cooked works well for these; broccoli, summer squash, greens (collard, mustard, chard, etc), and cabbage.