Preheat your oven to 375°F (190°C). Lightly grease a baking dish with butter. This helps prevent sticking and makes cleanup much easier later.

Wash and peel the potatoes. Slice them into thin, even rounds. Thin slices cook faster and create tender layers throughout the casserole.

Heat a large skillet over medium heat. Add the ground beef and diced onion. Cook until the beef is browned and the onion becomes soft and fragrant.

Drain excess grease from the skillet. Add salt, black pepper, and garlic powder. Stir everything together so the seasoning spreads evenly throughout the beef mixture.

In a mixing bowl, combine the cream of mushroom soup and milk. Whisk until smooth. This creamy mixture helps keep the casserole moist while baking.

Arrange half of the sliced potatoes in the baking dish. Spread half of the cooked beef mixture over the potatoes. Pour some of the sauce over the top.

Repeat the layers with the remaining potatoes, beef mixture, and sauce. Make sure the ingredients are spread evenly for consistent cooking and flavor.

Sprinkle the shredded cheddar cheese evenly over the top. The cheese melts beautifully and creates a golden, delicious topping during baking.

Cover the dish with aluminum foil and bake for 45 minutes. Remove the foil and bake for another 15 minutes until the potatoes are tender.

Let the casserole rest for about 10 minutes before serving. This helps the layers settle and makes slicing and serving easier.