1Heat oven to 350°F (325°F for dark or nonstick pan). Grease bottom only of 13x9-inch pan. In large bowl, beat cake ingredients with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour into pan.
2Bake as directed on box for 13x9-inch pan. Cool 15 minutes.
3In small bowl, mix espresso granules and 1/2 cup boiling water. Stir in corn syrup. Pierce top of cake every 1/2 inch with long-tined fork. Brush top of cake with espresso syrup. Cool completely, about 1 hour.
4In medium bowl, beat cream cheese and powdered sugar with electric mixer on low speed until mixed. Beat on high speed until smooth. Gradually beat in whipping cream, beating on high speed about 2 minutes or until stiff peaks form. Spread cream mixture over top of cake; sprinkle with cocoa. Store covered in refrigerator.