Grease and line a cake tin (roughly 20cm x 25cm). Half-fill a medium pan with boiling water and simmer over a low heat. Place a heatproof bowl over the pan of simmering water and melt the butter, chocolate and golden syrup together, stirring well.
Once the mixture is smooth, wrap the digestive biscuits in a clean tea towel and bash with a rolling pin into rough pieces, then add to the mixture. Add the dried fruit, walnuts, coconut flakes and marshmallows, then break in the meringue, reserving some for later.
Mix everything together until well combined then pour the mixture into the lined tin. Scatter over some coconut flakes, push in a few chocolate biscuits to make tombstones and dot pieces of meringue around the biscuits. Pop in the fridge for at least 2 hours, or until set. Once firm, remove from the fridge, carefully remove from the tin and finish with a dusting of icing sugar. Cut into squares and give out to trick or treaters.