Brown the ground beef and onion in a skillet until the meat is cooked through and onions are translucent, about 8–10 minutes.

Prepare the potatoes by washing and slicing them into 1/8-inch thick rounds, keeping them in cold water.

Layer half of the sliced potatoes in the greased crockpot, followed by half of the cooked beef mixture and half of the cheese. Repeat with remaining ingredients.

In a bowl, mix together the cream of mushroom soup, milk, garlic powder, salt, and pepper until smooth, then pour over the layered ingredients.

Cover and cook on low for 6–8 hours, checking halfway through for excess moisture.

In the last 15 minutes, add any remaining cheddar cheese on top to melt.

Garnish with fresh herbs and serve with sour cream if desired.