Remove tortillas from the refrigerator. Heat oven to 350 degrees. In a medium saucepan melt margarine; add onion and garlic to melted margarine, and sauté until tender. Stir in 1/2 of the olives, green chililes, sour cream and soup; mix well.  Divide soup mixture and set aside 3/4 cup in a small bowl, leaving remainder of soup mixture in saucepan. Add chicken and 1/2 cup of cheese to the sauce in the pan.

Warm the tortillas as directed on the package. Fill warm tortillas with chicken mixture; roll up. Place filled tortillas seam side down in ungreased 12 x 8 inch (2-quart) baking dish. In the small bowl with the remaining soup mixture add millk; mix well, spread soup mixture over tortillas. Bake 30 to 35 minutes or until bubbly. Plate the tortillas, sprinkle with cheese and black olives.