Melt Butter on 50% power in microwave enough to get it softened. Pour into a large mixing bowl.
Melt cream cheese in same container as butter on 50% power in 30 second increments, watching very closely to keep it from burning. Cream Cheese does not need to be liquid, it just needs to be softened enough to be able to be stirred. Pour into the same mixing bowl as the butter.
Add the Cream of Celery Soup, Chopped Onion, Sour Cream, Garlic, Pepper and Salt to that same bowl and mix well.
Then add potatoes and shredded cheese and mix carefully.
Spray crock or liner with pam and then pour mixture in crock.
Cover and cook on low for 8 hours or high 4-5 hours or until potatoes are tender.
If your Crock has a tendency to burn, you can stir this a couple of times to even out the heat.
Their is nothing in the dish that needs to be baked to a certain temperature, so stirring once or twice is no big deal, as you do lose a bit of heat that way.