Add the potatoes, stock and butter to your slow cooker.
Place a paper towel or kitchen towel over the top, to collect the steam, and cover.
Cook for 3-4 hours on high or 7-8 hours on low.
Add the half and half, sour cream, salt and pepper and mash until smooth.
Keep the potatoes on the "warm" setting until ready to serve.
Top with your favorite toppings - cheese, bacon, sour cream, chives, etc.