Egg, cheese and sausage strata (breakfast casserole) - chinese grandma

Ingredients

• 1 pound sausage (3/4 lb is also plenty)
• 6 eggs
• 1 teaspoon ground mustard
• 1/2 teaspoon salt
• 1/4 teaspoon pepper, or to taste
• 2 cups milk
• 2 slices bread, cubed (can use more for thicker casserole; this amount will give you a more custardy texture)
• 1 cup cheddar cheese, grated