In a large skillet over medium heat, add ground beef and cook for about 5–7 minutes, breaking it apart as it browns. Drain any excess fat before adding chopped onions and minced garlic. Sauté until the onions turn translucent, which should take an additional 3–4 minutes.

Transfer the browned beef mixture to your slow cooker. Add in the frozen diced potatoes, sweet corn, and Rotel tomatoes with green chiles. Pour in the cream of mushroom soup and the broth or milk, stirring thoroughly.

Sprinkle in the paprika, parsley flakes, chili powder, garlic powder, black pepper, and salt. Use a wooden spoon to incorporate the seasonings evenly throughout the casserole.

Cover the slow cooker with its lid and set it to low. Allow the casserole to cook for approximately 3 hours, checking occasionally.

In the final 15 minutes of cooking, add 1 cup of shredded cheddar cheese to the slow cooker. Stir it in gently to melt and integrate.

Once the cooking time is complete, give the casserole a final stir. Serve it hot, topped with any remaining shredded cheese and optional crispy fried onions or crumbled bacon.