You will need a good size mixing bowl. Spray the slow cooker with cooking spray.

Melt Butter in microwave enough to soften, without burning. Pour into mixing bowl. I use a Pampered Chef Micro Cooker to use in the microwave.

Melt the cream cheese in the same bowl in the microwave, as it will help keep it from sticking. Watch carefully that it doesn't burn. Cream cheese just needs to be soft so it will mix well. Pour into the same mixing bowl.

Add the Sour Cream, Salt, Pepper, Cream of Celery Soup, Minced Garlic and chopped onion and mix well.

Add potatoes and shredded cheese and mix carefully.

Pour or scoop into the slow cooker.

Sprinkle the top with extra pepper and shredded cheese. Cook on low for 8 hours. You can carefully stir once or twice to keep the sides from browning, but only carefully (you don't want to make mashed potatoes!).