Optional but tasty: In a skillet over medium heat, cook the bacon and onion until the bacon is crispy and the onion soft. Add the garlic and cook a minute more. Then transfer the whole mess to the slow cooker along with about 2 tbs of the drippings.
Add the potatoes, cayenne, mustard, and stock to the slow cooker, then cover and cook until the potatoes are tender. It should take about 4 hours on high, or 8 hours on low.
Using a potato masher, mash some of the potatoes in the pot to add some creaminess to the broth. Then stir in the shredded cheddar and cream. Let cook to warm through, about 10 to 20 minutes.
Serve, garnished with your favorite baked potato toppings, like freshly crisped bacon, more cheese, sour cream, or chives.