Peel and cut potatoes into even chunks
Place potatoes in a pot and cover with cold salted water
Bring to a boil and cook until fork-tender
Drain the potatoes well
Return potatoes to the hot pot for a minute to remove excess moisture
Mash the potatoes until smooth
Warm butter and milk or cream together
Add the warm butter and dairy gradually while mashing
Season with salt and black pepper
Add more milk or cream until the desired creaminess is reached
Serve immediately