Prepare chocolate cake mix according to package instructions, and pour into two 8 or 9" greased, floured rounds. When cooled, slice each layer in half. Wrap rounds in foil and freeze until ready to put cake together.
Mix powdered sugar with cocoa.
Take out 1 c. of chocolate powdered sugar mixture and make glaze by adding a small amount of warm water and mixing together.
Whip the cream until stiff. Add remaining chocolate powdered sugar mixture and fold into whipped cream.
Spread 1/3 of chocolate whipped cream on first cake layer. Put second cake layer on top. Repeat process; pour glaze over top layer of cake and allow glaze to dribble down sides. Refrigerate.