Break buttered bread into pieces and put in the bottom of a greased 9- by 13-inch pan.
Spread grated cheese over bread.
Add any extra goodies you choose and sprinkle over the cheese.
Pour combined milk, beaten eggs, salt and dry mustard over all.
Refrigerate AT LEAST over night; longer is okay.
Bake at 350 degrees for 1 hour. I usually leave the casserole covered with aluminum foil for the first 30 minutes and then remove the foil for the last 30 minutes of baking. The casserole is done when it is bubbling and lightly browned.