Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish with cooking spray or butter.

In a large skillet over medium heat, cook the ground beef and chopped onion until browned (6-8 minutes). Drain excess fat. Stir in minced garlic, salt, pepper, and paprika. Cook for 1 minute. Mix in cream of mushroom soup and milk until smooth.

Wash and peel potatoes if desired, then slice thinly (about 1/8 inch thick) for even cooking.

Layer the casserole: Place sliced potatoes at the bottom of the greased baking dish, top with half the beef mixture, and sprinkle with cheddar cheese. Repeat layers and finish with potatoes and beef mixture topped with cheese.

Cover the casserole with aluminum foil and bake for 60 minutes. Remove the foil for the last 15-20 minutes to create a bubbly, golden crust.

Let the casserole rest for about 10 minutes before serving to allow layers to set.