Brown the Ground Beef and Onions in a skillet over medium heat for 5–7 minutes until cooked and onions are translucent.

Prepare the Potatoes by washing and slicing them to about 1/8-inch thickness.

Layer the Ingredients in the crockpot with half of the sliced potatoes, then half of the beef and onions, followed by a portion of cheddar cheese. Repeat the layering.

Whisk the Sauce by mixing cream of mushroom soup, milk, garlic powder, salt, and pepper until smooth, then pour over the layered ingredients.

Slow Cook the Casserole on low for 6 to 8 hours, until potatoes are tender and cheese is melted.

Melt the Remaining Cheese by adding more cheddar cheese on top in the last 15 minutes of cooking.

Garnish and Serve with fresh parsley or chives on top before serving warm.