1. In a skillet over medium heat, cook ground beef and chopped onion until beef is browned and no longer pink, about 5–7 minutes. Drain excess fat.

2. Wash and slice potatoes into even 1/8-inch thick rounds.

3. In the crockpot, layer half of the potatoes, then half of the beef and onion mixture, followed by a portion of shredded cheese. Repeat with remaining potatoes, beef, and some cheese.

4. In a bowl, whisk together cream of mushroom soup, milk, garlic powder, salt, and pepper until smooth.

5. Pour the sauce evenly over the layers in the crockpot.

6. Cover and cook on low for 6 to 8 hours, or until potatoes are tender and cheese is bubbly.

7. About 15 minutes before serving, sprinkle remaining shredded cheddar cheese on top and cover to melt.

8. Garnish with fresh parsley or chopped chives before serving, if desired.