Prepare a 9x13-inch pan with softened butter. Tear the bread slices into 1-inch pieces of bread and cover the bottom of the pan with half of the loaf, fitting the pieces tightly together like puzzle pieces.

Layer the ground ham over the bread and then top with the cheese. Tear the rest of the bread slices into pieces and nestle them together over the ground ham but don't pack too tightly, but just so they fit together.

In a 1 quart measuring cup, whisk the eggs and milk until smooth. In a small bowl, take 1 tablespoon of the egg and milk mixture and use a fork to mix the dry mustard into it until smooth. Add the mustard mixture into the quart measuring cup and mix well so that all of the mustard is incorporated. Add the chopped parsley and whisk.

Starting at one end of the casserole, slowly pour the egg mixture over the the bread, evenly distributing the wet ingredients and making sure to get into the edges too. Cover with non-stick aluminum foil and refrigerate overnight.

Remove the foil and bake at 325° F for 50-60 minutes or until the eggs are set and bubbling. If the bread starts looking too brown, loosely tent the foil over the top of the casserole and continue to cook until the egg is set. Remove the casseroled from oven and let sit for 5-10 minutes before cutting and serving.