Heat oven to 350°F. Spray bottom of 13x9-inch pan with cooking spray.
Make brownie batter as directed on box. Stir in 0.5 cup chocolate chips. Spread in pan. Bake 22 to 25 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool completely, about 1 hour.
In large bowl, beat cream cheese, 1.5 cups powdered sugar, cocoa, 0.75 cup heavy whipping cream, and 1 teaspoon vanilla with electric mixer on medium speed until smooth. Spread evenly over brownies. Refrigerate about 2 hours or until set.
When ready to serve, cut brownies into 6 rows by 4 rows. In chilled medium bowl, beat 1 cup whipping cream with electric mixer on medium-high speed until slightly thickened. Reduce speed; beat in 3 tablespoons powdered sugar and 0.5 teaspoon vanilla. Increase speed; beat mixture until stiff peaks form.
Spoon whipped cream into decorating bag fitted with 0.5-inch star piping tip. In center of each brownie, pipe in tight circle to make rosette flower. Garnish rosettes with chocolate chips. Store loosely covered in refrigerator.
Notes
Store loosely covered in the refrigerator to keep the filling and topping set.