1Heat oven to 350°F (325°F for dark or nonstick pan). Grease bottom only of 13x9-inch pan with shortening or cooking spray. In medium bowl, beat cream cheese and sugar with electric mixer on low speed until smooth. Add egg and vanilla; beat until well blended. Set aside.
2Make brownie batter as directed on box. Spread three-fourths of the batter in pan. Spoon filling by tablespoonfuls evenly onto batter. Spoon remaining batter over filling. Cut through mixture several times with knife for marbled design. Sprinkle with chocolate chips.
3Bake 33 to 37 minutes or until toothpick inserted in brownie 1 inch from side of pan comes out almost clean. Cool completely, about 1 1/2 hours. For brownies, cut into 6 rows by 4 rows. Store covered in refrigerator.