Heat oven to 350°F. Spray bottom only of 9-inch square pan with cooking spray. In medium bowl, beat Filling ingredients with electric mixer on low speed until smooth. Set aside.Make brownie batter as directed on box. Fold in the chocolate morsels, Spread 2¼ cups of the brownie batter in pan. Spoon filling by tablespoonfuls evenly over batter. Spoon remaining brownie batter over filling. Cut through several times with knife for marbled design.Bake 38 to 42 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool 30 minutes on cooling rack. Refrigerate about 2 hours or until cooled completely. Cut into 3 rows by 3. Store covered in refrigerator.