Begin by making the chocolate ice cream. Mix together the milk, milk powder and sugar in a pan over a medium heat. Bring to a simmer, whisking regularly to prevent the mixture from sticking

Once simmering, remove the pan from the heat and stir in the dark chocolate until melted and fully combined. Pass the mixture through a fine sieve to remove any lumps, pouring into a plastic container

Chill for a few hours, then remove from the freezer and churn in an ice cream machine as per the manufacturer's instructions. Return to the freezer and chill until required

Repeat for the hazelnut ice cream, bringing the milk, milk powder and sugar to a simmer and adding the hazelnut paste. Blitz with an electric hand blender to combine, then pass through a sieve, chill and churn. Keep in the freezer until required

To make the chocolate sauce, place the double cream, sugar and water in a pan and bring to the boil over a medium heat. Remove from the heat and gradually whisk in the cocoa powder, mixing until smooth

Bring the mixture back up to the boil, whisking continuously. Once bubbling, remove from the heat and stir in the dark chocolate until melted and fully combined. Set aside to cool, then chill until ready to assemble

Preheat the oven to 180°C/gas mark 4. Line 2 baking trays with greaseproof paper

Next prepare the sugared hazelnuts. Spread the hazelnuts out across 1 of the baking trays and gently toast in the oven for a few minutes until golden brown and fragrant – be careful as the nuts can burn very quickly

Meanwhile, place the water in a small pan over a high heat. Add the sugar and, without stirring, allow the mixture to come up to 140°C on a sugar thermometer

Once at this temperature, add the hazelnuts straight from the oven and mix quickly over the heat until the sugar becomes dry and powdery. Remove the pan from the heat and tip the nuts out across the other, clean baking tray to cool

Before assembling the tartufo, remove the ice creams from the freezer and allow to soften slightly. Line 8 ramekins with a large square of parchment paper, making sure there is plenty of overhang – scrunching up the paper first can help to give a snug fit

Scoop a large spoonful of the chocolate ice cream into the base of each ramekin and use the back of the spoon to form a well in the centre

Fill the wells with 2 or 3 of the sugared hazelnuts and 1 teaspoon of the chocolate sauce. Cover with a spoonful of the hazelnut ice cream, pressing down with the spoon to fill all the gaps

Finally, cover the hazelnut ice cream with another spoonful of chocolate ice cream, making sure that the fillings are covered completely in the chocolate layer

Fold up the overhanging paper to cover the ice cream completely, twisting slightly to hold it in place, and chill in the freezer for at least 2 hours to set

To serve, remove the paper parcels from the ramekins and place on serving plates. Unwrap the paper to reveal the ice cream bombe, sprinkling over a liberal dusting of cocoa powder to finish