This is just yummy; nice and cheesy. And this is a healthier version than most. This would be nice to serve at a brunch. Not sure where I got the recipe. Note that standing time is not included in the preparation time.
Remove crusts from bread. Put 1/2 of bread in a 9 x 13-inch glass baking dish that has been sprayed with Pam. sprinkle with 1-1/4 cups cheese. Top with remaining bread.
Whisk the eggs and egg whites together. Add the milk, onion, dry mustard and salt; whisk again to combine. Gently pour over contents of baking dish. Top with remaining cheese and a sprinkle of paprika for color. Cover and refrigerate 1 hour or overnight.
Preheat oven to 350 degrees F. Bake in preheated oven 45 minutes or until golden. Let stand 5 minutes and serve.