Preheat oven to 375°F (190°C) and lightly grease a 9x13 baking dish.

In a skillet, heat olive oil over medium heat. Sauté onion and garlic until fragrant, then add ground beef and cook until browned. Drain excess fat.

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

Arrange half of the sliced potatoes in the baking dish. Season with salt and pepper.

Spread half of the cooked beef mixture over the potatoes, sprinkle with cheese, and pour half of the soup mixture on top.

Repeat layers with remaining potatoes, beef, cheese, and soup mixture.

Cover with foil and bake for 45 minutes.

Remove foil, add more cheese on top, and bake uncovered for 15–20 minutes until bubbly and golden.

Let rest for 10 minutes, garnish with parsley, and serve warm.