Turn on IP on normal saute mode. Add butter, let it melt. Now add garlic, bay leaf, and celery, saute for few seconds.
Then add chopped leek, potatoes, salt, pepper, thyme, and vegetable stock. Stir well.
Cover the IP with its locking lid, vent valve on the sealing position. Press the manual/pressure button and set the timer for 7 minutes under high pressure.
Let the pressure release naturally. Open the lid, take out the bay leaf. Using an immersion blender, blend the mixture well.