Peel and chop the potatoes into uniform 1-inch pieces for even cooking. Place the potatoes in a steamer basket or directly in the Instant Pot bowl.
1.5 pounds potatoes
Add 1 cup of water to the bottom of the Instant Pot. Insert the steaming basket with potatoes or place them directly in the pot if using the sauté mode temporarily. Secure the lid and set the vent to sealing.
1.5 pounds potatoes
Cook on high pressure for 10 minutes. Once the timer beeps, carefully release pressure using the quick release method. Open the lid and check if potatoes are fork-tender; they should be soft and easily pierced.
Remove the potatoes from the Instant Pot and transfer them to a bowl. Use a masher or fork to mash the potatoes until smooth and free of lumps. Add butter and warm milk as you mash, mixing until the desired creaminess is achieved.
1.5 pounds potatoes
Season with salt and pepper to taste. Continue mashing briefly to evenly distribute the seasonings. The final mashed potatoes should be fluffy with a slight sheen, with a smooth, creamy texture.
1.5 pounds potatoes
Serve hot as a side dish, garnished with herbs if desired. The mashed potatoes should be fluffy, smooth, and glossy, perfect for pairing with main courses.