Preheat your oven to 350°F (180°C) and line two baking sheets with parchment paper.

In a large mixing bowl, beat together room temperature unsalted butter, granulated sugar, and light brown sugar until light and fluffy.

In a separate bowl, whisk together all-purpose flour, unsweetened cocoa powder, salt, and baking soda.

Add the large egg and vanilla extract to the butter-sugar mixture and blend until just combined.

Gradually add the dry ingredients into the wet mixture in two batches, mixing on low speed until no flour streaks remain.

Fold in the semi-sweet chocolate chips until evenly distributed.

Using a rounded tablespoon, portion the dough onto the prepared baking sheets, spacing them about 2 inches apart.

Bake for 12-13 minutes, until the edges are set and the tops wrinkle slightly.

Remove from the oven, tap baking sheets against the counter to flatten, and let cool for 5 minutes before transferring to a wire rack.