Spray 9X13 pan and set aside. Cut or break up frozen waffles* and place in prepared pan. Top with cheese then mix eggs**, milk***, salt and mustard and pour over waffles*.
Cover with foil or plastic wrap and place in refrigerator overnight or for at least 8 hours.
In the morning, preheat oven to 375*, remove paper top and bake casserole for 45-60 minutes, until center is set.
*Frozen waffles can be replaced with frozen French toast as well. Very yummy.
**Try replacing eggs with Eggbeaters for a healthier version.
***One of my favorite things to do is replace milk with liquid coffee creamer, flavor of your choosing.