For the Milk Chocolate Gelato Base: Measure out the milk, then scoop out 2 tbsp (30 ml) and place in a small bowl. Set aside.

Pour the remaining milk in a medium saucepan, then add the heavy cream, milk chocolate, and sugar. Set over medium heat and whisk constantly until the milk chocolate and sugar are fully melted and incorporated. Remove from the heat temporarily.

Whisk the cornstarch into the reserved milk. Pour into the saucepan and whisk to combine. Return the mixture over medium-low heat and cook, whisking constantly, for 5 minutes. (The mixture will thicken slightly.) Whisk in the hazelnut liqueur, if using.

Pour the milk chocolate gelato base into a bowl and gently place a piece of plastic wrap directly over the surface to prevent a film from forming. Cool to room temperature, then refrigerate overnight. The milk chocolate gelato base must be thoroughly cool before churning: this will produce the smoothest, silkiest texture.

For the Hazelnut Butter: Using a stick blender or a mini food processor, grind the hazelnuts to a smooth butter consistency. Depending of the appliance you’re using, this can take between 3 to 5 minutes. You don’t need to add any liquid to facilitate the process, just some patience. Scrape down the container from time to time and keep grinding, you’ll get there.

Measure out the hazelnut butter to get 1/2 cup (125 ml). Store any remaining almond butter for tomorrow’s morning toast.

Whisk the hazelnut butter into the cool milk chocolate gelato base. Use a stand blender, a stick blender, or a food processor to fully combine and blend to a super smooth consistency. Strain, if desired, to remove leftover chunks, if any.

Pour the gianduja gelato custard into the bowl of an ice cream maker and churn according to the manufacturer's instructions. Stop the machine when the gelato is thick and icy but still easily spoonable.

Transfer the gianduja gelato to an airtight container and freeze until firm, about two hours. The gelato will keep, frozen, for up to two weeks. Always take this gianduja gelato out to room temperature 15 to 20 minutes before serving to soften it and make it easier to scoop.