Preheat the oven to 350°F (175°C) and grease a 9×13-inch baking dish with olive oil or butter.

In a skillet, brown the ground beef with the chopped onion until fully cooked. Drain excess fat, then stir in the minced garlic, salt, black pepper, and paprika.

In a bowl, whisk together the cream of mushroom soup and milk until smooth.

Layer half of the sliced potatoes on the bottom of the baking dish.

Spread half of the beef mixture over the potatoes.

Pour half of the soup mixture over the beef and sprinkle with 1 cup of cheddar cheese.

Repeat the layers with the remaining potatoes, beef, soup, followed by the rest of the cheddar and mozzarella.

Cover the casserole with foil and bake for 45 minutes.

Remove the foil and bake for an additional 15-20 minutes, until the potatoes are tender and the cheese is bubbly and golden.

Let the casserole rest for 5 minutes before serving.