Line a square baking tin with baking paper
Melt together the butter, chocolate and golden syrup in a large pot over a low heat.
Once melted, take off the heat and reserve 100g of the mixture into a smaller pot.
To the mixture in the larger pot add the biscuits, raisins, cherries and marshmallows stirring well until everything is coated. The mallows will go gooey at this stage - yum!
Transfer the mixture into a dish lined with baking paper and then pour the reserved melted chocolate on top.
Decorate with the extra marshmallows and sprinkles, if desired.
Place the dish into the fridge to set, for around 1 - 1.5 hours.
Once set, cut into manageable sized chunks and enjoy!