More gelato recipes: Blood-Orange Gelato, Gingersnap Gelato, Pistachio Gelato, Coconut Gelato, Ricotta Gelato, Mint Chocolate Chip Gelato.
Preheat oven to 350 degrees. Spread nuts on a baking sheet, and toast in oven 8 to 10 minutes. Let cool completely, remove skins, and coarsely grind.
Combine milk and ground hazelnuts in a medium saucepan. Bring to a gentle boil, cover, and remove pan from heat. Let steep 2 hours. Pass through a cheesecloth-lined sieve, pressing hard on solids. Reserve strained milk, and discard solids.
Combine egg yolks and sugar in the bowl of an electric mixer fitted with the paddle attachment. Cream at medium-high speed until very thick and pale yellow, 3 to 5 minutes. Return milk to a simmer.
Add half of the warm milk to egg-yolk mixture, and whisk until blended. Return new mixture to saucepan with remaining milk. Cook over low heat, stirring constantly, until mixture is thick enough to coat the back of a wooden spoon.
Have ready an ice-water bath. Remove saucepan from heat, and immediately stir in cream and Frangelico. Pass mixture through a sieve set over a medium bowl. Place bowl in ice-water bath, and chill.
Freeze in an ice-cream maker according to manufacturer's instructions.
Store in an airtight plastic container up to 2 weeks.