Breakfast Souffle

1 1/2 lbs link sausage
4 eggs
8 slices white bread
3/4 lbs sharp cheddar cheese
1/2 tsp prepared mustard
1/2 tsp salt
1 can cream of mushroom soup
1 cup sliced fresh mushrooms
3 cups milk

Cut off crusts of bread and cut into pieces and line the bottom of a 9x13 pan (use a pyrex pan, no metal). Fry sausage, drain well and place on top of bread. Grate cheese and spread over this. Whip eggs with 2 1/2 cups milk, salt and mustard then pour over casserole. Let stand all night in refrigerator.
Next morning-
make sauce of: 1 can soup
1 cup mushroom
1/2 cup milk
Pour over casserole and bake at 300 degrees for 1 1/2 hours uncovered.