Turn on the Instant pot to "Sauté" setting and cook bacon in a pot, keep stirring until the bacon is crisp. Remove the bacon from the pan and reserve about 1/4 cup bacon grease.
Add chopped onions and cook until the onions become translucent. Add garlic and give a quick stir for about 15 seconds. Turn off the ""Sauté" setting.
Add potatoes, chicken broth into the Instant Pot. Set the Instant Pot to "Manual" and adjust to "10 minutes".
When cooking is complete, use a natural release to depressurize and open the lid when it's ready.
Set the instant pot to "Warm" and remove about ⅔ of the soup and puree with a blender. Return the puree soup into the Instant Pot and stir.
Set the Instant Pot to the "Saute" setting and bring soup to a simmer. Add sour cream, reserved bacon pieces, and milk. Keep stirring until well-combined and until you reach the desired consistency. Add chicken broth if needed. Do not boil the soup after adding the dairy to prevent the soup from curdling. Season with salt and pepper as desired. Turn off the Instant Pot.
Serve with fresh herbs (green onion) and crispy bacon.