Add everything except the butter into your pressure cooker and give it a stir. Close the lid and make sure your valve is in the sealing position. Then set to high pressure for 22 minutes. It will take about 15-20 minutes for the pot to reach pressure.
When the timer is complete, allow your pressure cooker to naturally release for 10 minutes. After 10 minutes, quick release the remaining pressure by setting the valve to the venting position, and open the lid once safe to do so.
Stir in the butter if using it and taste and add salt and pepper if needed. Serve garnished with fresh parsley and/or Parmesan cheese.
Notes
Give yourself enough time. Although the cooking time is set to 22 minutes, it will take an additional 15-20 minutes to reach pressure, and then 10 minutes of natural release time.Leftovers keep refrigerated in a sealed container for 3-4 days. Reheat on the stovetop, or use the sauté function on your Instant Pot.