Place half the ham in a 2-qt casserole. Cover with half the potatoes and half the onion. Sift half the flour over; season with salt and pepper. Repeat layering ham, potatoes and onion. Season with additional salt and pepper. Sift remaining flour atop. Pour milk over all. Bake covered at 350 till potatoes are nearly tender, 1 to 1 1/4 hours. Uncover. Combine bread crumbs and melted butter; sprinkle atop casserole. Top with parsley. Bake 15 minutes longer.