Press the Sauté button and add the butter and oil when the display reads "hot".
Add the leeks, stirring occasionally, and cook until soft (about 10 minutes).
Add the garlic and cook for about 30 seconds, until fragrant.
Add the potatoes, chicken broth, bay leaves, thyme, salt, pepper and red pepper flakes and stir to combine.
Put the lid on the pot and make sure the steam release knob is in the sealed position. Press the Manual (or Pressure Cook) button and set for 10 minutes.
When the Instant beeps to signal the end of cooking, naturally release pressure for 15 minutes. Manually release any remaining steam after 15 minutes.
Remove the thyme sprigs and bay leaves.
Using an immersion blender, purée the soup until smooth.*
Add the heavy cream and stir to combine. Taste and add salt and pepper if desired.**
Garnish with chives and black pepper and enjoy immediately. To freeze, follow the instructions above.