Grease and line a 7" round cake tin.
Crush the digestive biscuits into fine crumbs using a food processor, or by putting them in a plastic bag and bashing with a rolling pin.
Add the butter, golden syrup and cocoa powder to a saucepan.
Melt everything together slowly over a very low heat, stirring frequently.
Once the butter has melted and everything is well mixed, stir in the raisins and cherries.
Take the pan off the heat and stir in the crushed biscuits, mixing thoroughly.
Transfer the mixture into your lined tin and push it down firmly with the back of a spoon to create a level bottom layer.
Melt your chocolate (in 30 second bursts in the microwave to prevent burning). If creating the marbled topping with milk, white and dark, melt these in three separate bowls.
Pour the milk chocolate over the biscuit layer and smooth this out evenly to fully cover biscuit. Next, use a spoon to place random, alternating dollops of white and dark chocolate all over the top of the milk chocolate layer. Then use a skewer or cocktail stick to make swirling motions through the chocolate, creating a marbled effect.
Place the tin in the fridge for 2 hours.
Once set, the chocolate biscuit cake can be kept at room temperature. Slice, top with extra glacé cherries if desired, and enjoy! This can be stored in an air tight container for up to a week.