Beat the chocolate spread or frosting to soften it slightly, then spread it over the tops of the cooled cakes using a small palette knife.
Knead the green icing on a work surface lightly dusted with icing sugar. Roll out thinly and cut out 12 rounds using a 5 cm (2 inch) cookie cutter. Place a green round on top of each cake.
Shape 12 small golf tees from the white ready-to-roll icing. Lay one on top of each cake, securing with a dampened paintbrush. Press a foil-wrapped chocolate golf ball into the icing, alongside the tee, to finish.