Make Butter Cake. Let cool completely. Trim the tops of the 2 cakes. Cut each cake in half, creating 4 level rounds.
Place one layer of cake onto a cake board or serving platter. Using a piping bag with a 1-2cm nozzle, pipe frosting on top, add the second layer of cake, pipe frosting on top and continue with the 4 layers of cake. Frost the top and sides of cake.
A turntable/lazy susan will come in helpful. (Poor Susan!)
Using a large scraper, smooth the frosting on the top and sides of the cake. Refrigerate for at least 1 hour.
Ganache Drip;
Place chocolate and cream into a saucepan and melt together over a low heat, stirring, until nearly all of the chocolate has melted. Take it off the heat and continue to stir until all the chocolate has melted.
Pour ganache into a piping bag with a 1cm round nozzle. Pipe around the perimeter of the top of the cake allowing drips to fall down the sides. Working quickly, before it sets, pipe ganache over the whole top of the cake. Use a small spatula to smooth it out before it sets. Refrigerate.
Decorate as desired.