In the bowl of a stand mixer fitted with the whisk attachment, whisk eggs on high speed until light and pale in color, about 2 minutes. Reduce speed to low, and slowly add sugar, melted butter and vanilla extract. Continue mixing just until all ingredients are combined. On low speed, add flour mixture in 2 additions and mix just until combined and a dough starts to form. Fold in chocolate chips and toasted hazelnuts (see post for directions on how to toast hazelnuts).

On a lightly floured surface, with slightly wet hands, form dough into a ball. Divide into 2 equal pieces. Shape each half into a 14x2.5-inch rectangle and place them on the baking sheet, spacing them 4 inches apart. Bake for 25 minutes or until slightly risen, firm to the touch, and the top begins to crack. Let cool on a wire rack for 30 minutes. Using a serrated knife, cut logs into ½-inch slices. Return slices cut-side up to the pan in a single layer. Place pan in the oven and bake for 15 minutes until crisp. The longer they stay in the oven, the harder they become. Allow cookies to cool completely on a wire rack.

Cookies keep in an airtight container at room temperature for up to a week. They can be frozen for up to 2 months and thawed overnight in the fridge or for two hours at room temperature.