Preheat the oven to 350˚ F. Line baking sheets with parchment paper or silicone baking mats. In the bowl of an electric mixer, combine the butter and sugar. Beat together on medium-high speed until light and fluffy, 2-3 minutes. Blend in the eggs one at a time, scraping down the bowl as needed. Mix in the cocoa powder until well blended. Add the flour, salt and baking powder to the bowl and mix on low speed just until incorporated. Fold in the chocolate chips. Transfer the dough to a work surface and knead briefly by hand to be sure the ingredients are well combined.

To make giant cookies divide the dough into 12 equal pieces or for regular size cookies just roll about a golf ball size amount of dough. Roll each portion of dough into a ball and just slightly into a disc. Place on the prepared baking sheets, a few inches apart. Bake 16-20 minutes for giant cookies and 9 to 11 minutes for regular sized cookies. Let cool on the baking sheets 5-10 minutes, then transfer to a wire rack to cool completely.