Place the water on the bottom of the Instant Pot.
Add the potatoes and seal the lid.
Cook on manual pressure for 10 minutes. Let the pressure naturally release for 5 minutes and then release the valve to let the pressure fully release.
While the potatoes are cooking, brown the butter.
Add the butter to a medium saucepan and cook over low heat until brown specks begin to appear on the bottom of the pan. A light colored pan works best for this and, depending on the quality of your butter, this will take about 10 minutes. Try not to stir it and be patient!
Drain the potatoes and return to the Instant Pot.
Add all but 2 tablespoons of the butter, sour cream, milk, salt, and pepper.
Mash the potatoes. I prefer using a potato ricer or a masher to mash my potatoes, but you can use a mixer - just be careful not to over beat!
Serve drizzled with additional brown butter. Enjoy!