Brown sausage in a skillet over medium heat until there is no pink left. Drain the sausage on a paper towel lined plate to remove excess fat. Let cool.
Mix cracked eggs, milk, cheese, mustard, salt, and sausageinto a big mixing bowl until combined. Add the cubed bread and gently mix. Pour into a greased 9 by 13 pan.
Leave overnight in the fridge covered with tin foil. Preheat oven to 325. Bake uncovered for one hour until cheese is melted and the top is golden brown. Let cool for 10 minutes before serving.
Notes
Katie's Tips:*Substitute bacon for the sausage. Use crumbled up cooked, crispy bacon that has been laid out on a paper towel to get rid of the excess grease. *Sub spicy cheese like pepper jack for a kick.*To add some vegetables, sauté some onion and peppers and cool them. Add them to the egg mixture and combine before adding to the 9 by 13.