Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with olive oil or butter.

In a skillet, brown the ground beef with the chopped onion until fully cooked, then drain excess fat.

Stir in the minced garlic, salt, pepper, and optional paprika for a kick.

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

Layer half of the sliced potatoes in the baking dish, followed by half of the beef mixture, half of the sauce, and then sprinkle with 1 cup of cheddar.

Repeat the layers with the remaining potatoes, beef, sauce, and top with the rest of the cheddar and mozzarella.

Cover 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 it rest for 5 minutes before serving.