PREPARATION:

1. Preheat oven to 350°F. Grease 8-inch square baking pan; set aside. Beat butter and brown sugar in large bowl until light and fluffy. Add 1 cup flour. Beat until well blended. Stir in pecans, if desired. (Mixture will be crumbly.) Press evenly into prepared pan. Bake 15 minutes.
2. Place chocolate chips in small microwavable bowl. Microwave on HIGH 1 to 2 minutes or until melted, stirring after 1 minute. Beat cream cheese and granulated sugar in medium bowl until light and fluffy. Add remaining 1 tablespoon flour, egg and vanilla; beat until smooth. Gradually stir in melted chocolate, mixing well.
3. Pour cream cheese mixture over partially baked crust. Return to oven; bake 15 minutes or until set. Remove pan to wire rack; cool completely. Cut into 2-inch squares. Sprinkle with powdered sugar.