Remove white papery skin from garlic head (do not peel or separate cloves). Rub oil over garlic head; wrap in foil. Bake at 375° for 1 hour; cool 10 minutes. Separate cloves; squeeze to extract garlic pulp. Set aside. Discard skins.
Place potatoes in a saucepan, and cover with water. Bring to a boil; cook 15 minutes or until very tender. Drain. Heat milk in pan over medium heat until hot (do not boil). Add potatoes, salt, and pepper, and beat at medium speed of a mixer until potato mixture is smooth. Add garlic pulp, and stir well.
Mashed Potatoes With Sage: Omit garlic; add 2 tablespoons minced fresh sage to milk, salt, and pepper.
Chive-and-Goat Cheese Potatoes: Omit garlic; add 3 tablespoons minced chives and 1/2 cup (2 ounces) crumbled goat cheese to milk, salt, and pepper.