Fireman’s Overnight Breakfast Casserole With Country Gravy

Ingredients

• 1 pound ground breakfast sausage
• 4 cups sharp cheddar cheese, grated
• 12 eggs
• 1 large onion, chopped
• 1 red bell pepper, chopped
• 1 cup heavy whipping cream
• 1/4 cup green onion, chopped
• 8 oz sliced mushrooms
• Kosher salt and freshly ground pepper, to taste
• 2 cups milk
• 1/4 cup all-purpose flour
• 1-2 tablespoons butter or oil