Place the potatoes and garlic cloves in a large pot, cover with cold water by 1 inch, and add 1 tablespoon salt.

Bring to a boil, then reduce to a simmer and cook 18 to 20 minutes until the potatoes slide easily off a fork.

Drain well and return the potatoes and garlic to the hot pot, letting them sit 1 minute to steam off excess moisture.

Mash the potatoes and garlic with a potato masher until mostly smooth.

Fold in the warm milk, butter, sour cream, salt and pepper, stirring just until incorporated and creamy, since overmixing makes them gluey.

Taste, adjust the salt, and serve warm.