Preheat the oven to 350 degrees and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, cocoa powder, baking soda and salt.
In the bowl of an electric mixer, cream the butter and sugar until light and fluffy, 1-2 minutes. Scrape down the sides of the bowl with a rubber spatula.
Add the eggs, one at a time, scraping down the bowl and mixing well after each addition. Beat in the vanilla.
Add the dry ingredients and chocolate chips and stir on low speed until just combined.
Using your hands, split the dough in half and shape it into two logs about 3/4 inch high and 2 inches wide. Place them on the prepared baking sheet allowing them enough space to spread while they bake.
Bake them for 30 -35 minutes until the logs are firm to the touch.
Let them cool on the pan for about 5 minutes. Then, using a sharp knife slice the logs diagonally into 3/4 to 1 inch slices. (a little crumbling is ok)
Turn them on their sides, so that the cut sides are down.
Return them to the oven for 10 minutes. This will crisp up the biscotti.
Remove them from the oven and cool. Store in an airtight container until ready to enjoy with a cup of tea, cocoa or coffee.
Substitute a dairy free butter product or vegetable oil for the butter and use a dairy free chocolate chip.