Make-Ahead Breakfast Casserole

INGREDIENTS

• 2 1/2 cups seasoned croutons
• 1 pound spicy pork sausage
• 4 eggs
• 2 1/4 cups milk
• 1 (10.75 ounce) can condensed cream of mushroom soup
• 1 (10 ounce) package frozen chopped spinach - thawed, drained and squeezed dry
• 1 (4.5 ounce) can mushrooms, drained and chopped
• 1 cup shredded sharp Cheddar cheese
• 1 cup shredded Monterey Jack cheese
• 1/4 teaspoon dry mustard
• 2 sprigs fresh parsley, for garnish