Wash the fish heads in cold water and make sure there is no blood. Pat it dry.
In a heated pan, add oil and lightly sear the fish heads.
Cut the vegetables and add to the pressure cooker.
Add the fish and the thyme sprigs.
Add water until it reaches the 3 qt in the pressure cooker (or should just cover the fish)
In the Instant Pot, make sure the knob is on "sealing". Next, press "soup", leave the pressure on "high" and manually press the time to "45 minutes".
When the cooking time is done, turn the pressure cooker off immediately and let the pressure release naturally for 15 minutes before turning the knob to "venting", and removing the lid.
Strain the vegetables and the fish.
Recipe Notes
The cook time does not include the amount of time that it takes for the Instant Pot to get up to pressure