Preheat oven to 350 degrees. Line baking sheets with parchment paper and set aside.
Whisk flour, sugar. baking soda, cocoa powder and salt in a large bowl and set aside.
Cream butter and sugar until well combined. If using a stand mixer, this usually takes 1 minute. Add eggs and beat well.
Add in all dry ingredients into with creamed butter, the dough will be stiff. Halve dough and form into 12 by 2 inch logs, slightly flattened. Place on a baking sheet 4 inches apart or using separate baking sheets to bake the logs. Bake logs for 35 minutes, cool on a rack for 15 minutes, slice logs diagonally ( 3/4 inches) place biscotti back on baking sheets , cut side down and bake for another 15 minutes or until crisp. Cool and store.