Brown ground beef and onion in a skillet over medium heat. Drain excess grease.
Layer potatoes, then the beef and onion mix, in a slow cooker.
Whisk cream of mushroom soup, milk, salt, and pepper in a bowl. Drizzle over the beef and potato layers.
Cook: 6-8 hours on low or 4-5 hours on high.
An hour before serving, top with cheese and bread crumbs.
Cook until cheese is molten and golden.
Serve hot and savor the melding of rich flavors.
