1. Preheat your oven to 375°F (190°C). Grease a 9×13-inch casserole dish with butter.

2. Peel and thinly slice the potatoes. Dice the onion.

3. In a large skillet over medium heat, brown the ground beef. Add diced onion, garlic powder, salt, and pepper. Cook until onions are softened. Drain excess fat.

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

5. Layer half of the sliced potatoes in the prepared casserole dish.

6. Add half of the cooked beef mixture on top.

7. Pour half of the soup mixture evenly over the beef and potatoes.

8. Sprinkle 1 cup of shredded cheddar cheese over the layer.

9. Repeat the layers: potatoes, beef, soup mix, and the remaining cheese.

10. Cover the casserole with foil and bake for 45 minutes.

11. Remove foil and bake uncovered for an additional 20-25 minutes, until potatoes are tender and top is golden.

12. Let the casserole rest for 10 minutes before slicing and serving.