Stove Top: Peel and dice the potatoes; rinse well. In a 5 qt. sauce pan on medium/high heat, add the potatoes and just enough water to cover the top of the potatoes. Bring to a rolling boil and cook for about 20-30 minutes, or until soft enough to mash. Remove from heat; drain well. Add the butter, salt, and pepper. With a hand mixer, mash/blend the potatoes for about 30 seconds on medium speed. Add the desired amount of milk and continue to mash/blend to desired texture. Serve hot. Electric Pressure Cooker Version: Peel and dice the potatoes into semi-large chunks; rinse well. Add 1/2 cup of water to the cooker. Pour in the potatoes. Add the butter and season with salt and pepper. Cover and make sure the vent is set to closed. Press the Fish/Vegetables Steam button and the Time Adjustment button for a total time of 6 minutes. When timer goes off, use the quick release lever to release the pressure. If using a stainless steel pot, you can finish preparing in that pot. Otherwise, pour into separate bowl and mash with a hand mixer or masher, adding milk as needed.