Bake sourdough bread as directed.
Cube bread and place it in the bottom of a 9x13 glass dish.
Top the bread with the shredded cheddar cheese.
Layer the ham on top of the cheese and bread.
Pour melted butter over everything.
Whisk together the eggs, milk, salt, pepper, and dry mustard.
Pour milk mixture over the top of the bread.
Sprinkle Parmesan cheese on top.
Allow the casserole to sit in the fridge for at least 6 hours or overnight.
Bake at 350°F for 1 hour or until bread is bubbly and brown on top.
Serve warm.