Preheat your oven to 350°F (175°C). In a large skillet over medium-high heat, cook the ground beef and chopped onion until the meat is no longer pink. Drain excess fat, then stir in garlic powder, parsley, salt, and pepper.

In a greased 9x13-inch baking dish, arrange half of the sliced potatoes in an even layer. Top with half of the seasoned beef, half of the mushroom soup, and half of the cheese. Repeat layers with remaining ingredients.

Cover with foil and bake for 1 hour. Remove foil, sprinkle with any remaining Cheddar, and bake uncovered for an additional 10–15 minutes until cheese is bubbly and golden.