01 - 
                Preheat oven to 350°F. Grease a 9x3-inch round cake pan; then, line the pan with parchment paper. (You could also use GOOP*, a homemade pan release.)
              
              
              
                02 - 
                In a large bowl, combine the cake mix, 1 egg (reserving the other 2 eggs for later), and 1 stick of melted butter. Stir until well blended.
              
              
              
                03 - 
                Pour the mixture into the prepared pan, gently patting it down, and set aside.
              
              
              
                04 - 
                In the bowl of a stand mixer on medium speed (or using a hand-held mixer), beat the cream cheese until smooth. Add the remaining 2 eggs and the cocoa powder.
              
              
              
                05 - 
                Reducing the mixer to low speed, add the confectioners' sugar. Slowly add the remaining stick of melted butter. Add vanilla and continue to beat the mixture until smooth.
              
              
              
                06 - 
                Pour the filling into the pan, over the cake mixture. Bake for 40-50 minutes, being careful not to overbake the cake. The center should still be a little gooey when finished baking.
              
              
              
                07 - 
                Let the cake partially cool on a wire rack before cutting and serving.