Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper. In a large mixing bowl, cream together the softened butter, granulated sugar, cocoa powder and brown sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract, ensuring that it is evenly distributed throughout the dough.
Whisk together the all-purpose flour, baking soda, and salt in a separate bowl. Gradually add this dry mixture to the wet ingredients and stir well until combined. Be careful not to overmix, which can lead to a tougher cookie.
Fold in the semisweet chocolate chips and chopped nuts, if desired. Using a cookie scoop or spoon, drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart. This allows room for the cookies to spread as they bake.
Place the baking sheet in the preheated oven and bake for approximately 10-12 minutes or until the cookies are golden brown around the edges. The centers may appear slightly undercooked but will firm up as the cookies cool. Once the cookies have cooled completely, indulge in their irresistible deliciousness.