Peel and cut the potatoes into 2-inch chunks. Put them into an Instant Pot® along with 3/4 cup water and 1 teaspoon salt.
Lock the lid and set the lever to seal. Press "manual" and set for 10 minutes. When done, manually release the steam.
Remove the lid, leaving the pot in "keep warm" mode. Start mashing the potatoes. Add the butter, cream cheese, milk and ranch powder. Mash again until the potatoes are smooth. Taste and adjust the seasoning with salt, pepper or more ranch. Thin with more milk if needed. Serve hot garnished with chopped chives. The potatoes will keep warm in the pot for up to 30 minutes.