Scrub, peel potatoes and quarter the potatoes, trying to keep all the same size so they all cook at the same time. Place in a pot of cold water, then remove the water and refill the pot to remove extra starch, filling the pot until the potatoes are just covered.
Set the pot on medium-high heat and cook uncovered until you can easily pierce with a fork, about 20 minutes. Strain the water from the potatoes, retaining the water if you have a need for potato water. Leave the potatoes in the pot.
If mashing by hand, add the butter and start mashing then slowly add the warmed stock and milk until you get the right consistency for you.If you use a potato ricer, rice the potatoes first and then add the wet ingredients.