Take out the sour cream, milk, and butter and let them come down to close to room temperature, they shouldn’t be cold when added to the potatoes.
Peel the potatoes and cut them into thirds or fourths of equally-sized pieces.
Add them to the instant pot. Combine the chicken broth, water, and salt and pour enough liquid in to ensure that the potatoes are covered, don’t go over the max line inside the instant pot.
Cover and press the “manual” or “pressure cook” button and set the timer for 10 minutes.
Once the timer goes off, release the seal valve on the pressure cooker and wait for the steam to escape.
Ensure that the potatoes are fork tender. Reserve a ½ cup of the liquid and drain the rest. Use the liquid only if they are being kept warm and will be eaten later. The liquid can help them from becoming dry.
Add the butter. Use a potato masher to mash the potatoes until smooth, don't over-mash the potatoes or they will become gluey instead of creamy.
Stir in the sour cream and milk.
Take a taste before adding more salt. Keep warm in the instant pot until ready to eat!
Top them with freshly chopped chives/parsley if desired and enjoy!