Cut the bacon into 1 inch pieces and cook it over medium-high heat in a medium skillet. Cook until the bacon until crispy, remove from the pan, placing on a plate lined with paper towels. Reserve the bacon fat.
Add the diced onion to the pan in the bacon grease and cook until tender, about 2-3 minutes.
To a 6 quart crockpot add the potatoes, cooked onion, chicken broth, salt, and black pepper and stir to combine.
Place the lid on the slow cooker and cook on high for 4 hours or 6-8 hours on low 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.
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 cup cheese and 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 the soup topped with cheese, green onions and the bacon.