In a skillet over medium heat, cook the ground beef along with the chopped onion until the beef is fully browned and no pink remains, about 5 to 7 minutes. Drain any excess fat.

Wash the potatoes and slice them evenly to about 1/8 inch thick.

Begin by layering half of the sliced potatoes in the bottom of your crockpot. Add half of the cooked beef and onion mixture followed by some shredded cheddar cheese. Repeat these layers until all ingredients are used.

In a separate bowl, whisk together the cream of mushroom soup, milk, garlic powder, salt, and pepper until smooth. Pour this mixture evenly over the layered ingredients.

Cover the crockpot and let it cook on low for 6 to 8 hours, or until the potatoes are tender and the cheese is bubbling.

About 15 minutes before serving, sprinkle the remaining shredded cheddar cheese on top. Cover again until melted. Garnish with fresh parsley or chopped chives before serving.