Break the biscuits into smallish pieces. Wash the glace cherries of their sticky coating, dry and chop into smallish pieces.
Melt the butter in a saucepan. Add the cocoa and sugar to the pan and mix together, then add the dried fruit, broken biscuits and chopped glace cherries. Mix until all ingredients are combined.
Line large tins (the tins you could normally use for your sponges) and pour in the mixture. Press down with the back of a spoon and place in the fridge for about 2 hours.
Break the chocolate into pieces and melt over an indirect heat (in a bowl set over a pan of simmering water). Pour the melted chocolate over the top of the chiled mixture and spread using a palette knife.