Brown the Beef: In a large skillet, cook the ground beef, onion, and garlic over medium heat until the beef is browned. Drain any excess fat.
Combine Ingredients: Transfer the beef mixture to a slow cooker. Add the cream of mushroom soup, milk, diced tomatoes with green chilies, kidney beans, frozen corn, chili powder, salt, and black pepper. Stir until well mixed.
Add the Potatoes: Layer the thinly sliced potatoes over the beef mixture, stirring slightly to coat them in the sauce.
Slow Cook: Cover and cook on LOW for 6–7 hours or HIGH for 3–4 hours, until the potatoes are tender.
Add Cheese: In the last 20 minutes, sprinkle shredded cheddar cheese on top, cover, and let it melt.
Serve: Scoop onto plates and enjoy warm!