Make the gelato base according to the Classic Ice Cream Method. Add the gianduja while the base is still hot; whisk thoroughly to completely dissolve the gianduja.
Strain the base through a fine-mesh strainer and cool the base over an ice bath. Age the base under refrigeration overnight.
Once the base has aged, churn to the desired consistency.
Harden for at least 2 hours and up to 4 hours. Reserve until needed.