Preparation

Line 2 large rimmed baking sheets with parchment paper.

In a food processor, process 2/3 cup of the hazelnuts until finely ground, being careful not to turn them into hazelnut butter. Coarsely chop the remaining 1 cup hazelnuts.

In a large bowl, whisk together the oil, brown sugar, granulated sugar, and vanilla. Whisk in the egg and egg yolks. Sprinkle the salt and baking soda over the bowl. Vigorously whisk until incorporated. Using a flexible spatula, gently fold in the finely ground hazelnuts, flour, chopped hazelnuts, and chopped chocolate.

Divide the dough into 3-Tbs. portions, and roll into balls. Place on a large baking pan. Freeze for 1 hour.

While the dough chills, preheat the oven to 350°F. Place 10 balls of chilled dough on one of the parchment-lined baking pans. Bake until lightly browned, about 15 minutes, rotating halfway through the baking time. Repeat with the remaining 10 dough balls and the second parchment-lined baking pan.