Put the rack in middle of oven. Preheat oven at 400°F.
Cut the superior part of each garlic head. Put individually on a sheet of foil paper and oil with 1 tablespoon of oil. Close the foil paper on them. Cook in oven about 50 minutes or until garlic is tender and caramelized. Squeeze the cooked garlic head to let come out a garlic puree. Set aside.
Meanwhile, in a saucepan, brown the onion in remaining oil. Deglaze with the wine and let reduce by half. Add chicken stock and garlic puree. Bring to boil and let simmer about 5 minutes. Add salt and pepper.