Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper or silicone baking mats.

In a large mixing bowl, cream together the softened butter and sugar until light and fluffy. This should take about 3-5 minutes using an electric mixer.

Beat in the eggs one at a time, followed by the vanilla extract, ensuring each is well incorporated before adding the next.

In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Avoid overmixing to keep the cookies tender.

Fold in the chocolate chips or chunks until evenly distributed throughout the dough.

Using a cookie scoop or spoon, drop dough balls onto the prepared baking sheets, spaced about 2 inches apart. Flatten them slightly with your hand or the back of a spoon.

Bake in the preheated oven for 8-10 minutes, or until the edges are set but the centers are still soft.

Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.