1-Preheat the oven: Preheat the oven to 350°F and line a large baking sheet with parchment paper.

2-Mix dry ingredients: In a large bowl, mix the flour, baking powder, baking soda, and salt, then sift in the cocoa powder and whisk to blend evenly.

3-Whisk wet ingredients: In a medium bowl, whisk the eggs, gradually adding the sugars until smooth and slightly lightened; stir in the vanilla extract and melted butter.

4-Combine wet and dry: Create a well in the dry ingredients, pour in the egg mixture, and stir gently until the flour is mostly absorbed.

5-Fold in additions: Fold in the roasted hazelnuts and coarsely chopped dark chocolate, using hands if necessary.

6-Shape dough: Divide the dough into two portions, shape each into a 10-inch log about 2 inches wide, and place them on the baking sheet.

7-First bake: Bake for 25 minutes until puffed, shiny, and slightly cracked. Allow to cool for 30 minutes, then reduce the oven temperature to 300°F.

8-Slice logs: Slice the logs diagonally into pieces about ¾ inch thick using a sharp serrated knife.

9-Second bake: Arrange the slices on the baking sheet and bake for 10-15 minutes until dry and crisp. Let cool completely.

10-Dip in chocolate: Melt the dark chocolate and dip each biscotti halfway, then let it set on parchment paper.