Wash, peel, and chop the Russet potatoes into cubes. 1-2 inches works well.
Peel and rough chop the onion, if you don't want to completely blend the soup, cut the onion pieces smaller.
In a 5 quart or larger slow cooker, add the potatoes, onion, chicken broth, garlic, salt, and pepper.
Cook on high for 4 hours or low for 6-8 hours until onions and potatoes are tender.
When cook time is up, remove lid, add cream cheese, cheddar cheese, and cream. Using a potato masher, mash the potatoes and blend the soup together until desired consistency is reached. You can also use an immersion blender for a super smooth loaded potato soup.
Add more milk, cream, half and half, or chicken stock for a thinner soup.
Top with your choice of garnish and toppings to make it "loaded"