Fill a very large pot halfway with cold water and two tablespoons of fine sea salt.
Place potato pieces into the pot as you peel and chop them.
Bring to a boil over high heat, then reduce heat and and simmer until tender, about 10 minutes.
Drain potatoes in a colander.
Heat the butter and milk together in a small pot over medium-low heat until butter is melted.
Either press the potatoes through a ricer or food mill back into the pot, or return them to the pot straightaway and use a masher to mash them until smooth.
Pour in hot buttery milk in a slow stream, stirring to incorporate.
Taste and adjust for salt and pepper. Don't be shy with the seasoning.
