Grease a large (at least 9x13) baking dish with butter, oil or cooking spray and heat a skillet over medium high heat.
Cook the bacon and sausage
Cook the sausage, (breaking up small) until fully cooked.
Remove the sausage and drain the grease, then cook the bacon until crisp.
Make the filling
In a large bowl, add the eggs, milk, mustard, salt and pepper and whisk until well combined.
With a wooden spoon, mix in the shredded potatoes, half of the cheese the cooked sausage and half the bacon (keep half the crumbled bacon for serving).
Pour everything into the greased baking dish
Cover with foil or plastic wrap, and refrigerate overnight.
When ready to bake:
Preheat oven to 350 degrees F.
Remove the cover from the dish add the remaining cheese to the top.
Cook the casserole for 45 minutes (up to an hour) until the center is set and not jiggly.
Remove from the oven and allow to cool slightly before serving.
Sprinkle with remaining bacon crumbles and green onions.
What to do with leftoversCover and store leftovers in the refrigerator for up to 4 days. Reheat until it is piping hot!Substitutions/AdditionsIf you don't have Dijon mustard, you can use dry mustard powder instead, or leave it out.You can use all bacon, all ham, or all sausage. Or a combination of all of them!Add in some chopped bell peppers (I like red peppers, but yellow and green are cool too) for some extra flavor.If you are into a southwestern flair (and who isn't?) then a can of green chilis or a chopped jalapeno is fantastic in this.Freezing instructionsThis recipe can be frozen before baking.Cover tightly with plastic wrap and foil. Label and freeze. Thaw overnight and bake as directed in the morning.