Butter a 20 x 5cm deep square baking tray and line with baking parchment. Melt the chocolate and butter in a heatproof bowl over a pan of simmering water, ensuring the base of the bowl doesn’t touch the water. Stir occasionally until fully melted and smooth.

Mix the custard creams, pistachios, dried cherries and marshmallows into the melted chocolate mixture, reserving a little of each to decorate later, until evenly coated. Tip the rocky road mixture into the prepared tray, smooth the surface with the back of a wooden spoon, then poke the reserved ingredients and jazzies into the top and scatter with the sprinkles. Chill in the fridge for at least 2 hrs until firm, or overnight.

Run a sharp kitchen knife under a hot tap, wipe dry, then cut the rocky road into 16 squares. Will keep in an airtight container for up to two weeks.