Butter and line a 20cm square tin, or use a 20cm square silicone mould. Break the biscuits into pieces – they need to be no smaller than a pea, but not too chunky or your rocky road won’t hold together.
Halve any larger nuts either by snapping them or carefully cutting with a knife, then combine them with the biscuits. Halve any large pieces of dried fruit and chop or snap sweets into smaller pieces, then add these to the bowl.
Melt 300g of the chocolate, the butter and the golden syrup carefully in a pan set over a low heat, stirring occasionally, then pour this over the biscuit and nut mixture and mix together so the chocolate covers everything.
Tip the mixture into the tin, then level the top – it doesn’t need to be completely smooth. Melt the remaining chocolate in the microwave in short blasts, or in a heatproof bowl over a small pan of simmering water, then drizzle this over the top and sprinkle with the decorations. Chill for at least 3 hrs or overnight before cutting into squares. Will keep in the fridge for three to four days.