INGREDIENTS
1 1/2 cups
Onion
1 10 ounce package
Spinach, frozen
9
Eggs, large
2 tbsp
Dijon mustard
1/2 tsp
Black pepper
1/4 tsp
Nutmeg
1 tsp
Salt
8 cups
(1 inch) french or italian bread
3 tbsp
Butter, unsalted
6 oz
Gruyere
2 3/4 cups
Milk
2 oz
Parmigiano-reggiano