Preheat the oven to 350°F. Line 2 or 3 baking sheets with parchment paper.

With an electric mixer, cream together the butter and sugar, about 3 to 4 minutes, until smooth.

Add the eggs and vanilla and beat until combined.

Add the flour, cocoa, baking soda, and salt and mix, until a dough forms. (It should hold together easily but not be too sticky.) Stir in the chocolate chips.

Roll the dough into 1-2" balls and place them 2" apart on the prepared baking sheets. (You can make larger cookies, but you’ll need to place fewer on a pan and bake them a little longer.)

Bake for 8 to 10 minutes, until the edges are set and the centers are just a tiny bit glossy. (They will set on the hot pan as they cool.)

Let the cookies cool on the baking sheet for at least 10 minutes before removing them from the pan to cool completely.