Cut off pointed end of garlic bulbs; place garlic on a piece of aluminum foil, and drizzle with oil. Fold to seal.
Bake at 425 degrees for 30 minutes; cool. Squeeze pulp from garlic; set aside.
Cook bacon in a large skillet until crisp; remove bacon, and drain on paper towels, reserving 2 Tbsp drippings in skillet. Crumble bacon, and return to skillet; add green onions. Cook 1 minute or until green onions are tender. Set aside.
Peel half of potatoes; cut into ¼” pieces. Cut remaining unpeeled potatoes into ¼” pieces.
Cook potatoes in a Dutch oven in boiling salted water to cover 20 to 25 minutes or until tender; drain and place in large bowl.
Add roasted garlic pulp, bacon mixture, sour cream, 1 C cheese, and next 4 ingredients; mash with a potato masher until blended. Spoon potato mixture into a lightly greased 13x9” baking dish; top with remaining ½ C cheese.
Bake at 350 degrees for 10 minutes or until cheese melts. Garnish, if desired, with chives.
Yield: 8 to 10 servings.