Place the dark and milk chocolate pieces into a heavy-based pan. Add the butter and golden syrup and cook over a low heat to melt and combine.
Place the amaretti biscuits into a freezer bag and bash with a rolling pin to make crumbs of various sizes.
Place the Brazil nuts into another freezer bag and bash in the same way.
Take the pan of melted chocolate mixture off the heat and add the crushed biscuits and nuts.
Add the glacé cherries and mini marshmallows. Fold the mixture carefully to coat all of the solid ingredients with the syrupy chocolate mixture.
Pour the mixture into a 25cm/10in x 30cm/12in greased and lined baking tray and smooth the surface as much as possible (although it will look bumpy).
Refrigerate for two hours, or until firm enough to cut. Dust with icing sugar, then sprinkle with edible glitter if you wish.
Remove the block of rocky road from the tray and cut into 24 rectangles.