Garlic Mashed Potatoes

Roasted garlic and rich sour cream give these mashed potatoes a creamy twist. 2-1/4 pounds russet potatoes 1 whole garlic bulb 1 tablespoon olive oil 1/2 cup sour cream 2 tablespoons butter 1/8 teaspoon salt 1/8 teaspoon black pepper fresh chives, cut into small...