Step 1

START: Fill a large bowl with water. Quarter the potatoes lengthwise, then slice about 1/2 inch thick; add the slices to the water as you go. after all the potatoes have been sliced, drain in a colander set in the sink and rinse briefly under cool water. Drain well, shaking the colander to remove as much water as possible. On a 6-quart Instant Pot, select More/High Sauté. Add 4 tablespoons of butter and let melt. add the potatoes and 1 teaspoon salt, then stir until the potatoes are well coated. stir in 1/2 cup water, then distribute in an even layer.

Step 2

FAST:Press Cancel, lock the lid in place and move the pressure valve to Sealing. Select Pressure Cook or Manual; make sure the pressure level is set to High. Set the cooking time for 9 minutes. When pressure cooking is complete, quick-release the steam by moving the pressure valve to Venting. Press Cancel, then carefully open the pot.

Step 3

FINISH: If there is liquid remaining in the pot, select More/High Sauté and cook, stirring often, until no moisture remains. Press Cancel to turn off the pot. Using a potato masher, mash the potatoes directly in the pot until mostly smooth with some large bits. add the half-and-half and continue to mash to the desired consistency. Fold in the remaining 2 tablespoons butter until melted. Taste and season with salt and pepper.