Preheat the oven to 350 degrees Fahrenheit. Line two baking sheets with parchment paper.
Cream together the butter and sugars in a large bowl for a couple of minutes, until the butter is light and fluffy, a stand mixer with a paddle attachment is best.
Add the eggs and vanilla and mix in until just combined.
Add the 2 1/2 cups flour, baking powder, baking soda, and salt and stir them to combine it into a soft cookie dough.
Separate the dough into two equal portions.
Add the remaining 1/4 cup of flour to one section of the dough, and work it in completely.
Add the cocoa powder to the other section of the dough, and work it into the dough evenly and completely.
Mix chocolate chips into each of the cookie dough sections.
Take about 1 TBS of each dough, squish them together and roll them into a smooth ball.
Place the cookie balls onto the prepared baking sheet, at least 2 inches apart from each other.
Bake the cookies for 8 to 11 minutes, or until the edges are set and the tops have started to crack.
Let the cookies cool on the baking pan for 5 minutes before transferring them to a cooling rack to cool completely.