Heat the cream until it just comes to a simmer. Remove from the heat. Place the chocolate in a heat-proof bowl. Pour the cream over the chocolate. Allow to sit for about 10 to 15 seconds. Then, whisk until the chocolate is melted and the mixture is smooth. Allow to cool slightly, stirring occasionally. Mixture should be a little thick, but still pourable.
Place the cake on a metal rack set over a sheet pan. Pour the chocolate ganache over the cake and smooth the top and sides with a palette knife. Let set for 1 hour.
Yield: about 3 cups