Slice the ends off of the squash. Then cut the squash in half lengthwise and then cut each of those in half widthwise, and then those in 2, until you have a total of 8 pieces.
1 large butternut squash
Scoop out the seeds in the center cavity of the squash. Cut them once again in halves, leaving you with a total of 8 sections that are similar in size.
Place the trivet inside your Instant Pot and add 2 cups of water.
2 cups water
Add in the butternut squash on the trivet and close the lid.
Set the cook time for 15 minutes on high pressure.
Once cook time has elapsed, release the vent and open the IP when the steam is gone.
Remove the squash from the IP and gently remove the skin from the squash.
With a fork or a potato masher, mash the squash until you the lumps are gone and you get the texture you would like. If you want it smoother you can also use an electric mixer, but I suggest leaving a bit of texture into your mashed butternut squash.
Continue by placing the squash into a large bowl. Add in the butter, so it melts into the mixture.
5 Tablespoons butter
Continue by adding the salt, pepper, sour cream, mix until combined and serve.
Salt to taste, Pepper to taste, 2 Tablespoons sour cream
Optional: garnish with fresh rosemary, chives, or basil.
Optional: Chives