Preheat the Oven and Prepare the Cookie Sheets - Preheat the oven to 350 degrees Farenheit. Line your baking trays with parchment paper, or if you want, silicone mats.
Combine the Cocoa Powder, Flour, Baking Powder and Salt - In a medium mixing bowl, whisk together the cocoa powder, flour, baking powder, and salt. Set the mixture aside.
Cream the Butter and Sugar - In a large mixing bowl, cream together the butter and sugar until a smooth mixture forms. You can use an electric mixer or beat the mixture by hand using a whisk. It will be easier to cream the mixture with an electric mixer.
Combine the Flour Mixture and Butter Mixture - Gradually combine the flour mixture into the butter mixture, beating well.
Add Chocolate Chips and Chopped Nuts If Desired - Gently fold the chocolate chips into your chocolate cookie dough. If desired, fold in chopped nuts as well.
Bake the Cookies - Drop cookie dough by rounded teaspoons onto your cookie trays. Bake in the oven for 8-10 minutes. Let the cookies cool on the cookie sheets for a few minutes before transferring to the wire rack to cool completely before serving.