Saute the onions and celery in the oil until tender, but do not over brown them. Stir in the cranberry sauce, sour cream and vinegar. Bring to a boil and cook 15 minutes or until thickened.
Heat the oven to 375?. Stack the four sheets of phyllo pastry, spraying each layer with Pam as you go. Cut the dough into 18, 3" squares. (Each square will be 4 layers thick).
Press each square into a a greased mini muffin or mini tart pan. Place one piece of cheese in the center of each and top with some of the cranberry filling. Bake 12-15 minutes or until the pastry is golden. Serve warm.