Step 1

Line a 28 x 18cm baking tray or glass dish with parchment paper and set aside.

Step 2

Put both chocolates, the butter, golden syrup and salt into a large heatproof bowl set over a saucepan of gently simmering water (taking care that the base of the bowl is not touching the surface of the water). Heat for 2-3 minutes, stirring often, until completely melted and combined.

Step 3

Add the sultanas, rum, biscuits and three-quarters of the pistachios (try adding the larger bits here, leaving the more powdery bits to finish) to the chocolate. Using a spatula, combine everything together until the biscuits and nuts are completely coated in chocolate. Transfer to the prepared tray, smoothing the top with the spatula so that it’s flat and even, then sprinkle the remaining 25g pistachios on top. Set aside for 10 minutes to cool, then wrap tightly with plastic wrap. Refrigerate for 2-3 hours, until completely set.

Step 4

Cut into bars – you should get If not serving straight away, store them in an airtight container and serve fridge-cold.