Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the finely chopped onion and sauté for 3-4 minutes until translucent and fragrant.

Add 1 pound of ground beef, seasoning with salt, pepper, and garlic powder. Cook for 7-10 minutes until browned. Drain excess fat.

In a greased baking dish, layer half of the cooked beef mixture, then half of the thinly sliced potatoes, topped with half of the cream of mushroom soup mixed with ½ cup of milk.

Sprinkle half of the 2 cups of shredded cheddar cheese over the soup mixture. Repeat layering with the remaining beef, potatoes, soup mix, and top with the remaining cheese.

Cover the dish with aluminum foil and bake at 350°F (175°C) for 45 minutes.

Remove foil to crisp the cheese and bake for an additional 15-20 minutes until golden brown.

Let the casserole rest for about 10 minutes before serving.