Grease a 16 x 26cm (base size) slice pan. Line base and sides with baking paper, allowing the paper to overhang 2cm above the long sides.

Place dark chocolate in a microwave-safe bowl. Microwave, stirring every 30 seconds, for 1-2 minutes or until melted and smooth. Pour into the prepared pan and use a spatula to spread evenly over the base. Arrange half the wafers and half the marshmallows over the top. Place in the fridge for 10 minutes or until the chocolate has set.

Meanwhile, to make the pistachio filling, use your hand to crush cereal biscuits into a frying pan. Cook over medium heat, stirring constantly, for 2-3 minutes or until golden. Transfer to a bowl and set aside to cool slightly.

Process pistachios in a food processor until finely crushed. Add crushed pistachio and pistachio spread to the toasted cereal biscuits and stir until well combined. Spoon on top of the dark chocolate layer and use the back of a spoon to smooth the surface. Place in the fridge for 20 minutes to set.

Place milk chocolate in a microwave-safe bowl. Microwave, stirring every 30 seconds, for 1-2 minutes or until melted and smooth. Set aside for 5 minutes to cool slightly. Pour over the pistachio layer and smooth the surface. Arrange remaining wafers, marshmallows and chopped pistachio over the top. Place in the fridge for 30 minutes or until set.

Transfer the rocky road to a serving board. Stand for 10-15 minutes to soften slightly, then use a large knife to cut into pieces. Serve.