In a large bowl, cream together butter, sugar and eggs.

In a separate bowl, sift together all dry ingredients: flour, cocoa powder, and baking powder.

Slowly add the dry ingredients into the wet ingredients. Mix until a dough forms. Fold in hazelnuts.

Wrap the dough in plastic and chill for 10 minutes.

Preheat oven to 375 degrees and line a baking sheet with parchment paper.

Form the biscotti dough into a log, about 8 inches in long and 3 inches wide. Bake for 25 minutes.

Remove from the oven and cut into strips (width-wise) on a diagonal, about 1 inch wide.

Turn down the oven to 325 degrees and bake for 12-14 minutes or until completely cooked through. Allow to cool on a wire rack.