First, place your peeled and sliced potatoes into your Instant Pot. Pour in the chicken stock and water, then add 1 teaspoon of salt. Make sure the liquid mostly covers the potatoes; if not, add a little more water. Give them a quick stir to distribute the salt.
Secure the lid on your Instant Pot and set the pressure valve to 'Sealing'. Cook on 'Manual High' pressure for 12 minutes. Once cooking is complete, carefully switch the valve to 'Quick Release' to let out all the steam.
Once the pressure is fully released, open the lid and drain any remaining liquid from the pot. Use a potato masher to mash the potatoes until they are wonderfully smooth and fluffy.
While the potatoes are cooking, gently warm the unsalted butter and half-and-half (or whole milk, if you prefer a lighter option) in a small saucepan or microwave until the butter is fully melted.
Pour this warm mixture over your mashed potatoes. Stir well, then add the sour cream, the remaining 1 teaspoon of kosher salt, and the ground black pepper. Mix until everything is beautifully combined and creamy. Taste and adjust seasonings if you like!
Transfer your comforting mashed potatoes to a serving bowl. A small dab of extra butter and a sprinkle of black pepper can be a nice finishing touch!
Serve these easy, healthy-ish mashed potatoes hot and enjoy every delicious bite!