Caramelized Onion with gruyere

1 -2 onion , peeled and sliced 1 (10 ounce) box frozen spinach , thawed 1 cup gruyere , grated 4 eggs 1 1/2 cups milk (or cream) nutmeg salt and pepper canola[...]

I’m always a sucker for a good breakfast casserole. Anything I can whip together the night before and then pop in the oven first thing in the morning?[...]