Fry sausage and drain. Reserve fat.
Place sausage in lightly greased 9” x 13” baking dish.
Crumble the bread by hand.
Sauté the apples in the reserved sausage fat.
Combine the bread, apples, mustard, eggs, cheese, and milk and mix well.
Pour the mixture over the sausage, cover, and refrigerate overnight.
Preheat the oven to 350º fahrenheit. Bake the casserole covered for 30 minutes. Uncover and bake another 30 minutes.
Allow to cool for 10 minutes. Serve immediately.