Hazelnut gelato is made by blending roasted hazelnuts into a cooked custard base, then churning it in an ice cream maker until smooth and dense. Roasting the hazelnuts before blending deepens their flavor considerably. From start to finish, including freezing time, expect to set aside about four to five hours.
Prepare Hazelnut Base: In a blender or food processor, add the toasted hazelnuts and blend until a fine paste forms. If necessary, add a small splash of milk to help achieve the desired consistency.
Make the Custard: In a medium saucepan over medium heat, combine the milk and cream. Heat until just simmering, but do not bring to a boil. Remove from heat and set aside.
Whisk Egg Yolks: In a mixing bowl, whisk together the sugar and egg yolks until the mixture is pale and slightly thickened.
Combine Ingredients: Slowly pour the warm milk mixture into the sugar and egg yolk mixture, stirring constantly to prevent curdling. Return the mixture to the saucepan and cook over low heat, stirring constantly, until it thickens slightly and coats the back of a spoon, about 8-10 minutes.
Infuse Flavor: Stir in the hazelnut paste and vanilla extract into the custard. Mix well to combine. Strain through a fine-mesh sieve into a clean bowl to remove any solid particles.
Chill and Churn: Let the mixture cool to room temperature, then cover and refrigerate until thoroughly chilled, at least 4 hours or overnight. Once chilled, churn the mixture in an ice cream maker according to the manufacturer's instructions.
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Notes
For an extra smooth texture, ensure all hazelnuts are finely ground.
To add a unique twist, try adding a splash of Frangelico liqueur during the churning process for a deeper hazelnut flavor.