Cut the bacon into 1-inch pieces and cook the bacon in a large skillet over medium-high heat until crispy. Remove the bacon from the pan and place it on a paper towel-lined plate. Reserve the bacon for the soup topping.
Discard all but 1 Tablespoon of the bacon fat from the pan.
Cook the onion in the bacon fat until the onion is tender and translucent, about 3-4 minutes.
ASSEMBLE AND SLOW COOK SOUP:
To a 6 quart or larger slow cooker, add the potatoes, cooked onion, chicken stock, salt, and black pepper and stir to combine.
Place the lid on the slow cooker and cook on HIGH for 4 hours or on LOW for 6-8 hours or until the potatoes are fork-tender.
When the potatoes are tender, use a potato masher or immersion blender to slightly mash about half of the potatoes. The more you mash, the thicker the soup will be.
TO FINISH:
In a small jar with a lid, shake the cream and cornstarch until smooth, about 1 minute.
Pour cream mixture into the crockpot with 1 ½ cup shredded cheddar cheese and the sour cream. Stir to combine well.
Place the lid back on the crockpot and let the soup warm through on high, about 20 minutes or until thickened.
SERVE:
Serve the soup topped with bacon, green onions, and shredded cheddar cheese.