To make the icing, beat the butter, sugar, 1 tbsp milk and the vanilla until soft and fluffy, adding the rest
of the milk if it’s too stiff. Transfer 4-5 tbsp of the icing to a piping bag fitted with a 1cm round nozzle and
pipe a border around the cake, leaving a 1cm gap between the edge and the border. Pipe on the halfway
line, centre circle and penalty areas, then squeeze any remaining icing from the bag back into the bowl of
icing. Dye the remaining icing green using a few drops of food colouring gel. Transfer the green icing to a
piping bag fitted with a 1-2cm star nozzle, or grass/hair nozzle. Pipe small blobs of icing all over the cake,
avoiding the pitch lines, until the sponge is completely covered. Decorate with mini figures and a chocolate football, if you like. Will keep in an airtight container at room temperature for up to four days.