Place the metal trivet in the insert of your Instant Pot. Add 1 cup of water.
Wash sweet potatoes clean and slice them lengthwise. Place them on the trivet cut side up. It's okay to stack them up on each other.
Close the lid, turn the valve onto "sealing" position, press manual or pressure cooker setting and set the timer to 14 minutes. The Instant Pot will beep after a few seconds and it will start cooking.
Once the time is up, let the Instant Pot release the pressure naturally. Carefully open the lid and remove the potatoes from the IP. I remove the trivet and pour the remaining water out. Then I scoop the flesh out of the potatoes, discarding the skin.
Add brown sugar, salt, butter and vanilla and mash with a potato masher, a whisk or even use a hand mixer.
My potatoes were medium size, from 6" to 8" in circumference.