Butter a 2 1/2 quart casserole dish while heating a large skillet over medium high.
Add 1 1/2 pounds breakfast sausage and brown for five minutes mincing it up as it cooks.
Add 2 cups sliced mushrooms and a 1/2 cup finely chopped onions and cook for another five minutes, stirring often.
In a large bowl, combine 4 eggs (lightly beaten) and 2 cups milk.
Take one large loaf of day-old Italian bread and cut into 18 to 20 slices, buttered if desired.
Layer one third of the bread in bottom of casserole dish and top with half of the sausage mixture.
Sprinkle with 1 1/2 cups of cheddar cheese (we like to vary the cheese from Mexican blend to Monterey Jack).
Repeat another layer then cover with a third layer of bread.
Pour the egg mixture, slowly, over the entire dish so it will soak into all layers.
Top with another layer of cheese and let stand for at least one hour or refrigerate overnight until next morning.
Do not let stand in refrigerator longer than 24 hours.

Bake at 350 degrees on a baking sheet on the lowest rack until bubbly and golden brown.

Enjoy!