In a medium bowl, add to sifter the flour, cocoa powder, baking soda, and salt. In the bowl of an electric mixer beat the butter, granulated sugar, and brown sugar until creamy, about 2 minutes. Add the vanilla and eggs. Gradually beat in the flour mixture. Stir in the chocolate chips. If time permits, wrap dough in plastic wrap and refrigerate for at least 24 hours but no more than 72 hours. This allows the dough to “marinate” and makes the cookies thicker, chewier, and more flavorful. Let dough sit at room temperature just until it is soft enough to scoop. Divide the dough into 3-tablespoon sized balls using a large cookie scoop and drop onto prepared baking sheets. Bake until golden brown. Cool for 5 minutes before removing to wire racks to cool completely.