Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.

In a large bowl, cream the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add the egg, vanilla extract, and milk to the butter mixture. Mix until smooth.

Gradually add the dry ingredients to the wet mixture, stirring until just combined. Avoid overmixing.

Fold in the chocolate chips.

Scoop tablespoon-sized portions of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake for 8–10 minutes, or until the edges are set. The centers will still look slightly soft.

Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.