Grease Pyrex 9 x 13 inch glass pan
2 c. seasoned croutons, on bottom of Pyrex
1 c. shredded Cheddar cheese, on top of croutons
Optional layer: 2 (4 ounce) cans mushrooms or chopped ham/Spam

Beat and pour over the above:

6 to 8 eggs
2 c. milk
1/2 tsp. salt
1/2 tsp. prepared mustard
1/8 tsp. onion salt
Dash of pepper

Bake at 325 degrees for 60 to 65 minutes until eggs are set.