Turn the Instant Pot on and click the "Saute" button (followed by the "start" button if your model requires it). Wait for the unit to fully pre-heat. Add the bacon and cook, stirring occasionally, until crisp (approx. 5-8 minutes).
Transfer the bacon to a paper towel lined plate with a slotted spoon, leaving the grease in the pot. Add the onion and cook, stirring occasionally, until the onions have softened and started to brown (approx. 5 minutes).
Add the kale and sauté for 2-3 minutes.
Add the garlic and cook for an additional 30-60 seconds, until fragrant.
Add the potatoes, chicken stock, salt, and black pepper and gently stir. Place the lid on the Instant Pot making sure the steam valve is in the closed position. Set the Instant Pot to Manual/Pressure Cook on High for 7 minutes.
When the Instant Pot has finished, carefully release the pressure manually by switching the valve to the “venting” position.
Remove the lid and set the Instant Pot to the Sauté Low setting. Add the heavy cream and butter. Stir to combine.
Remove 2 tablespoons of cooking liquid and add to a small bowl. Whisk in the cornstarch and then add the slurry to the soup.
Use an immersion blender (or let cool and transfer to a blender) and blend the soup to your desired consistency. If you like a chunky consistency, remove a few of the large potato chunks before blending. Add them back in before serving for a nice chunky texture.
Cook on the Sauté-Low setting for an additional 5 minutes, or until the soup has thickened to your desired consistency. Serve immediately. Garnished with extra bacon and cheese, if desired.