Begin by preheating your oven to 350°F (175°C). This ensures your cookies bake evenly and achieve that perfect texture.
In a medium bowl, whisk together the all-purpose flour, cocoa powder, baking soda, and salt. This step is crucial for evenly distributing the leavening agent and cocoa powder throughout the flour, ensuring a consistent flavor and texture.
In a large bowl, use an electric mixer to cream together the softened butter, light brown sugar, and granulated sugar until the mixture is light and fluffy. This usually takes about 2-3 minutes.
Add the egg and vanilla extract to the creamed butter and sugars. Beat until well combined, scraping down the sides of the bowl as needed.
Gradually add the dry ingredient mixture to the wet ingredients, mixing just until combined. Be careful not to overmix, as this can lead to tough cookies.
Gently fold in 1 1/3 cups of dark chocolate chips using a spatula. The dough will be thick and rich, packed with delicious chocolate.
Using a cookie scoop or a spoon, drop rounded tablespoons of dough onto a baking sheet lined with parchment paper, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers still look slightly soft. The cookies will firm up as they cool.
Remove the baking sheet from the oven and let the cookies cool on the sheet for 5 minutes before transferring them to a wire rack to cool completely.