1. Place potatoes in a large pot with 2 tablespoons salt and garlic. Add water to cover by 1 inch and bring to a boil. Then reduce heat to medium and simmer until potatoes are tender and can be pierced easily with a fork, 12 to 15 minutes.

2. Drain potatoes and garlic in a colander. Return to pot and cook over medium, stirring frequently, until pale, dry, and a film begins to form on bottom of pot, 2 to 3 minutes. Working in batches, press through a ricer into a large bowl, or mash directly in pot with a potato masher. Cover to keep warm.

3. In a small saucepan, combine milk, butter, and thyme. Cook over medium until butter melts and milk is steaming. Discard thyme, then stir milk mixture into potatoes. Season with salt and pepper, top with a pat of butter and more pepper, and serve.