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

2. In a large skillet over medium heat, cook the ground beef until browned and crumbly. Drain excess grease.

3. Add diced onion to the beef, season with salt, pepper, and garlic powder. Cook for another 2–3 minutes until onion is softened.

4. Wash and slice potatoes into ¼-inch thick rounds.

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

6. Begin layering the casserole:

7. – Layer half the potatoes

8. – Add half the beef-onion mix

9. – Pour half the soup mixture

10. – Sprinkle a bit of cheese

11. – Repeat all layers, topping with the remaining cheese.

12. Cover with foil and bake for 50 minutes.

13. Uncover and bake an additional 15–20 minutes until cheese is golden and potatoes are fork-tender.

14. Let rest for 5 minutes. Garnish with parsley if desired, then serve.