Position oven racks in the upper and lower thirds of the oven; preheat to 325°F. Line 2 large baking sheets with parchment paper.

In a large bowl, combine the flour and cocoa powder.  Mix the nibs and sea salt in a separate small bowl.

In a stand mixer, cream the butter and sugar on medium speed for about 5 minutes, until it is light and fluffy.  Add the vanilla extract. Reduce the speed to low; add about 1/2 of the flour-cocoa mixture and mix well, then add the remaining flour-cocoa mixture, stopping as necessary to scrape down the sides of the bowl. Increase the speed to medium and beat for 1 to 2 minutes. Stop the motor and fold in the nibs-salt mixture by hand until well distributed. The dough will be sandy and fairly stiff.

Lightly flour a work surface and rolling pin, or flatten the dough and place it between 2 large pieces of plastic wrap; roll the dough into a square 1/4-inch thick. Using a cookie cutter, cut out the cookies and place them about 1 inch apart on the baking sheets. 

Bake for 7 minutes, then rotate the baking sheets from top to bottom and front to back; bake for 8 minutes or until their aroma is apparent and the cookie bottoms are crisp. 

Let them cool on the sheets for 5 minutes, then transfer to a wire rack to cool completely.

STORE: In an airtight container for up to 1 week. The dough can be refrigerated, well wrapped, for up to 1 week or frozen for up to 2 months.