Peel the potatoes and cut them in quarters. Rinse and place in a pot of salted water (enough to cover the potatoes).
Bring water to a boil, then reduce heat and simmer, covered. Cook until tender, then drain.
Gradually add in the milk and use a potato masher or fork until the potatoes are well mashed, and the potatoes are at your desired consistency. Mix in the butter, then add the salt and pepper to your liking.