Rub the inside of a 4 quart heavy pot with the cut sides of the garlic, then discard. The garlic, not the pot. Add wine to pot and bring just to a simmer over moderate heat. Gradually add cheese to pot stirring constantly in a zigzag pattern (not circular) to prevent cheese from balling up, until cheese is just melted and creamy (do not let boil). Stir cornstarch into fondue. Bring to a simmer and cook, stirring for 5 to 8 minutes. Transfer to a fondue pot set over flame.