Peel and cube about 4 lbs of potatoes. Place the potatoes in the bowl of a slow cooker. Add 1 cup of butter (2 sticks) and salt, cover, and cook the potatoes for 3 ½ hours or until fork tender.
Heat half and half and milk in a saucepan until bubbles begin to form around the edges.
Add the milk mixture to the potatoes, mixing until combined. Stir in cream cheese until smooth and creamy.