1. In a skillet over medium heat, cook the ground beef, chopped onion, and minced garlic until the beef is browned and the onion is softened. Drain any excess fat from the pan.

2. In a bowl, stir together the condensed cream of mushroom soup and milk until the mixture is smooth and creamy.

3. Lightly grease your slow cooker and start with a layer of half the sliced potatoes. Top with the cooked beef mixture, kidney beans, diced tomatoes with green chilies, frozen corn, chili powder, salt, and black pepper. Pour the soup mixture over the top, then add the remaining potatoes.

4. Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the potatoes are tender and the flavors have had a chance to meld.

5. Sprinkle the shredded cheese of your choice over the top of the casserole and cover. Let the cheese melt for about 10-15 minutes before serving.

6. Scoop and serve this Slow Cooker Cowboy Casserole hot, with a side of cornbread or a fresh green salad for a complete and satisfying meal.