Peel the potatoes and cut them into evenly sized chunks for even cooking.
Place the potatoes (and garlic, if using) into a large pot and cover with cold water. Add 1 teaspoon salt.
Bring to a boil over medium-high heat and cook for 15 to 20 minutes, or until the potatoes are fork-tender.
Drain the potatoes well and return them to the warm pot.
Mash the potatoes gently until mostly smooth using a potato masher.
Add the butter first and let it melt into the hot potatoes.
Slowly pour in the warm milk while mashing until creamy and smooth.
Season with black pepper and additional salt if needed.
Serve warm with an extra pat of butter if desired.
