Cook the ground beef and chopped onion in a skillet over medium heat. Stir until the beef is browned and there is no pink remaining, about 5-7 minutes. Drain any excess fat.

Wash and thinly slice the potatoes evenly, about 1/8 inch thick.

In the crockpot, layer half of the sliced potatoes at the bottom. Add half of the cooked beef and onion mixture followed by a portion of the shredded cheddar cheese. Repeat these layers with the remaining potatoes, beef, and cheese.

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

Pour the creamy mixture evenly over the layered ingredients in the crockpot.

Cover the crockpot and cook on low for about 6 to 8 hours until the potatoes are tender and the cheese is melted and bubbly.

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

Garnish with fresh parsley or chopped chives before serving.