Use dry mustard powder if you don't have Dijon mustard, or leave it out altogether.It is possible to use all bacon, all ham, or all sausage. Or you can even use a combination of all of them!For some extra flavor, add some chopped bell peppers (red is my favorite, but yellow and green can also work). Cook the peppers first (with the bacon or sausage will work too).A can of green chilis or a chopped jalapeno would be perfect if you prefer a southwestern flair (and who doesn't?).
Overnight Breakfast Casserole Pioneer Woman, Overnight Breakfast Casserole