Place the cake on an 8-in/20-cm cardboard cake round. Reserve 4 oz/110 g of the butter-cream for décor and coat the top and sides of the cake with the remainder. Refrigerate until the buttercream is firm.
Glaze the torte with the warm ganache. Allow to set.
Mark the torte into 10 portions. Using a pastry bag fitted with a #5 plain tip, pipe a small do