Spray the pan very well with cooking spray. This will allow the cake to release much easier once it is baked. Don't fill the pan more then 2/3's full. It will rise once it bakes. Follow the baking time for the cake mix. Once the cake is done remove from the pan on to a cooling rack. The cake will need to cool completely before applying the icing.
While the cake is baking and cooling prepare the fondant. Take 1/3 of the fondant and kneed in color for the tassel. Roll it out to a long sausage shape and with a knife score it to look like a tassel. Roll a small ball look to like the knot used to attached the tassel.
Take the remaining fondant and add cocoa powder until you get a nice dark brown color. Use a little shortening on your hands if the fondant becomes sticky. Add the black food coloring. It is much easier to take fondant from brown to black then from white to black. Roll out the fondant out to cover the 8 inch cake board. Attach the tassel and knot to the covered cake board.
Ice the cake with a thin coat of buttercream frosting. Roll the fondant out to a 12 inch circle and place on top of the cake. Smooth the fondant down a little bit at a time working around the whole cake. When you have the whole cake covered cut the extra fondant off the bottom of the cake with a knife. Attach the 8 inch cake board with a little buttercream icing.
If you need this cake to feed more people add an 8 inch cake below the cap as I have done in the photo above. This cake can be covered in you choice of icing and decorated in the colors to match the grad's school. The diploma is white fondant rolled and red fondant cut to look like a bow.