01 - Place potatoes and garlic cloves in a large pot. Cover with cold water and add a generous pinch of salt.
02 - Bring to a boil over high heat, then reduce to a simmer. Cook for 15–20 minutes, or until potatoes are very tender.
03 - Drain well and return potatoes and garlic to the pot. Let steam dry for 1–2 minutes.
04 - Add butter, warm milk, sour cream (if using), salt, and pepper. Mash with a potato masher until smooth and fluffy.
05 - Taste and adjust seasoning as needed.
06 - Serve hot, garnished with parsley and an extra pat of butter if desired.