Heat oven to 350°F (325°F for dark or nonstick pan). Grease (or use cooking spray) bottom only of 9-inch square pan.
Make brownie batter as directed on box and spread in prepared pan. In medium bowl, beat cream cheese with electric mixer on low speed until creamy; beat in sugar, vanilla, and 1 egg until well blended. Drop by tablespoonfuls over brownie batter in pan. Cut through batter with knife several times for marbled design.
Cut brownies into bite-size pieces for mini desserts with maximum flavor.
To quickly soften cream cheese, unwrap the cream cheese, place in small microwavable bowl and microwave uncovered on High 10 seconds or just until softened.
