Set Instant Pot to sauté mode. Once hot, add butter. When the butter is melted, add chopped onion and saute for 3-5 minutes, until translucent. Season with salt and pepper. Add garlic and saute for about a minute. Add chicken broth to the pan and scrape up the brown bits at the bottom of the pot with a wooden spoon.
Add potatoes and seal on the lid. Set Instant Pot to manual pressure cook, high pressure, 15 minutes. Once cook cycle is over, quick release the pressure by turning the valve on the lid.
Remove the lid of the Instant Pot. Using an immersion blender, blend the potatoes.
Add cream cheese, sour cream, and half and half. Stir well, until cream cheese is melted. Add half of the cheddar cheese and half of the crumbled bacon and stir until cheese is melted.
Pour soup into bowls and garnish soup with remaining cheese, bacon, and chopped green onions.