Add the butter to your Instant Pot, then turn on Saute mode and allow the butter to melt.
Once the butter is melted, add the leeks and garlic to the Instant Pot, and saute while stirring frequently until everything has softened. It usually takes 8-10 minutes.
Next, add the chicken stock, white potatoes, bay leaves, fresh thyme, salt, pepper and garlic powder to the Instant Pot and stir to combine.
Place the lid on your Instant Pot, then turn on Soup mode for 15 minutes.
Allow the pressure to release naturally. Once the pressure has dissipated, remove the lid from the Instant Pot. Take the thyme stems and bay leaves out of the pan and discard.
Use an immersion blender to puree your Instant Pot Potato Leek Soup. Once it's smooth, stir in heavy whipping cream and turn the Instant Pot back on Saute. Allow the soup to come to a gentle simmer, stirring constantly.
If it's too thin, allow it too cook down a bit. If it's too thick, you can add more chicken stock or heavy whipping cream. Taste and adjust spices, if necessary. Serve garnished with chives.