This is a combination of a recipe for hazelnut gelato and chocolate ice cream. Basically I took the recipe for the hazelnut ice cream as a base, then reduced the amount of sugar and chocolate used in the chocolate recipe. I also added about 1/2 cup more of milk after steeping the hazelnuts, since they soak up a lot of liquid.
1 cup hazelnuts
1/4 cup sugar
2 cups cream
1 cup milk
2 oz unsweetened chocolate
3 tbsp unsweetened cocoa powder
4 egg yolks
1/2 cup + 2 tbsp sugar
1/2 cup milk (could go as high as 1 cup)
Toast the hazelnuts in the oven (350 for 10-15 minutes until they are golden and smell toasty). Peel by rubbing with a tea towel. Allow to cool completely, then grind them up with the 1/4 cup sugar in a food processor.
Heat ground hazelnut mixture with 2 cups cream and 1 cup milk and 2 oz hard chocolate. Once the hard chocolate has melted completely, whisk in the cocoa powder slowly so it doesn't clump. Bringl liquid just to a boil. Take off the heat, cover, and let steep for 1 hr.
Strain out hazelnuts with a fine strainer, pressing out all the liquid. Add extra 1/2 (or even 1 cup) cup milk and return to low heat. Meanwhile whisk together egg yolks and 1/2 cup + 2 tbsp sugar in a bowl. Temper the eggs with the heated milk mixture, then return to heat and let thicken. Chill and churn.
The chocolate and sugar are approximate. If you find it not sweet or chocolatey enough, add more.
Although I was skeptical at first that what was effectively hazelnut tea could impart a strong nut flavor, it's actually very strong, and also very delicious. The resulting flavor was very gourmet, and definitely as good as any store-bought chocolate hazelnut ice cream I've ever had.
Update: I modified this recipe to make hazelnut ice cream with a fudge ripple. Don't use the chocolate, cocoa powder, or 1/2 cup + 2 tbsp sugar. Instead use another 1/4 cup sugar whisked in with the egg yolks. When putting the finished ice cream into the freezer container, layer it with the cooled fudge ripple recipe, which I got from David Liebowitz, below:
1/2 cup sugar
1/3 cup light corn syrup
1/2 cup water
6 tbsp cocoa powder
1/2 tsp vanilla
Put all ingredients except vanilla in a medium saucepan and bring to a simmer over medium heat, stirring frequently. Once it reaches a simmer, cook for 1 minute, then chill completely. Drizzle over ice cream as you layer it into the freezer container. Tastes like the Hershey's syrup out of a can! Also it would be good drizzled over other desserts as a chocolate sauce.