Start by preheating your oven to around 200°C (390°F). Spread the hazelnuts evenly on a baking tray and roast them until they become deep golden brown.
Let them cool slightly, then remove the skins and chop them roughly. Roasting the nuts helps release their oils and enhances the overall flavor of the ice cream.
In a saucepan, combine the whole milk, cream, half of the sugar, vanilla paste, and salt. Heat the mixture over low heat until it begins to steam but not boil.
Add the chopped roasted hazelnuts into the warm milk mixture. Allow the nuts to steep for about one hour so their flavor fully infuses into the liquid.
After the infusion time, strain the milk mixture through a sieve into another saucepan. Press the hazelnuts gently to extract as much flavored liquid as possible.
Add the hazelnut paste, glucose syrup, and milk powder, then whisk until combined. Heat the mixture gently until steaming.
In a separate bowl, whisk the egg yolks with the remaining sugar until smooth. Slowly pour a small portion of the hot milk mixture into the yolks while whisking constantly.
This process is called tempering and prevents the eggs from scrambling. Once combined, pour the egg mixture back into the saucepan.
Cook the mixture over low heat while stirring constantly with a spatula. Continue cooking until the custard thickens and reaches about 82°C (180°F).
Remove it from the heat and blend briefly with a stick blender to create a smooth consistency. Then strain the custard again to remove any lumps.
Allow the custard to cool completely at room temperature. Once cooled, cover the surface with baking paper and refrigerate overnight.
This resting period helps develop deeper flavors and ensures the base is cold enough for churning.
Pour the chilled custard into your ice cream machine and start churning. The mixture will gradually thicken and become similar to soft-serve ice cream.
Most machines take around 30 minutes to reach this stage.
Melt the dark chocolate gently using a microwave or bain-marie until smooth. Transfer it into a piping bag for easy drizzling.
While the ice cream machine is still running, pipe a thin stream of melted chocolate into the ice cream. The cold temperature instantly freezes it, creating delicate chocolate shards.
Once the chocolate is mixed in, churn for about 30 more seconds. Transfer the ice cream into a freezer-safe container.