1. Preheat the Oven: Set your oven to 375°F and grease a 9×13-inch baking dish.

2. Cook the Beef: In a skillet, brown the ground beef with the chopped onion until the meat is fully cooked. Drain any excess fat and season the mixture with garlic powder, onion powder, salt, and pepper.

3. Layer the Potatoes: Spread half of the thinly sliced potatoes in the prepared baking dish.

4. Add the Beef: Spoon the seasoned ground beef mixture evenly over the potato layer.

5. Whisk the Sauce: In a bowl, whisk together the cream of mushroom soup and milk until smooth and creamy.

6. Repeat the Layers: Pour half of the soup-and-milk mixture over the beef layer. Top with the remaining potato slices, then pour the rest of the soup mixture over the top.

7. Top with Cheese: Sprinkle the shredded cheddar cheese evenly over the casserole.

8. Bake to Perfection: Cover with foil and bake for 45 minutes. Remove foil and continue baking for an additional 15-20 minutes, or until potatoes are tender and cheese is bubbly and golden-brown.

9. Serve and Enjoy: Allow to cool for 5 minutes before serving.