Line 13x9-inch pan with parchment, with ends of parchment extending over sides. Prepare cake batter as directed on package; pour into prepared pan.
Beat remaining ingredients with mixer until blended. Spoon over cake batter; swirl gently with knife.
BAKE 35 to 40 minutes or until toothpick inserted in centre comes out with clean. Cool completely. Use parchment handles to remove dessert from pan before cutting to serve.
