PREHEAT oven to 400°F. Cut thin slice off top of garlic head to expose cloves; discard top. Place garlic head on square sheet of foil; drizzle with oil. Wrap garlic loosely with foil. Prick potatoes in several places with fork. Bake potatoes and garlic 1 hour.

REDUCE oven temperature to 350ºF. Cut small slice off both ends of each potato. Cut potatoes crosswise in half. Scoop out centres, leaving 1/8-inch-thick shells. Place potato flesh in medium bowl; mash. Squeeze garlic out of papery shell into bowl with potatoes. Add sour cream, 1-1/4 cups of the shredded cheese and the Parmesan cheese; beat until fluffy. Spoon evenly into shells, mounding filling as necessary to use all the filling; place in shallow baking dish.

BAKE 30 min.; top with remaining 1/4 cup shredded cheese. Bake an additional 5 min. or until cheese is melted. Sprinkle with bacon.