Prepare and bake cake according to package directions, using two greased and floured 9-in. round baking pans. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a large bowl, beat cream until it begins to thicken.
Add confectioners' sugar; beat until stiff peaks form. In another bowl, beat cream cheese and butter until smooth. Gradually beat in confectioners' sugar, cocoa and vanilla.
Cut each cake horizontally into two layers.
Place bottom layer on a serving plate; top with a third of the whipping cream. Repeat layers twice. Top with remaining cake layer. Frost top with cream cheese mixture. Store in the refrigerator.
