Preheat oven to 350 degrees. Place hazelnuts on a baking sheet and bake until light brown, about 8 minutes. Cool. Line two large baking sheets with foil and spray the foil with nonstick cooking spray. Adjust the oven racks to divide the oven into thirds. In a food processor, combine 2 tablespoons of the hazelnuts, the flour, 2 tablespoons of the chocolate chips, the cocoa, espresso powder, baking soda and salt. Process until the nuts are finely ground. Transfer dry ingredients to a large bowl. In the same food processor, combine the sugar, eggs, egg whites and vanilla until slightly thickened, about 2 minutes. Add to the dry ingredients. Stir in remaining hazelnuts and chocolate chips. Spoon 1/4 of the batter (about 3/4 cup) into a rope about 14 inches long and 1 1/2 inches wide, on one side of the baking sheet. Repeat, with two ropes on each baking sheet. Bake, reversing sheets once, until firm, about 15 minutes. Cool 10 minutes. Reduce the oven to 300 degrees. Place the logs on a cutting board. With a serrated knife, cut into 1/2-inch slices, about 80 biscotti. Place the slices upright on the baking sheets, 1 inch apart. Bake until the cut sides feel dry to the touch, 20 to 25 minutes. Cool completely on a wire rack. Store in an airtight container.
