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

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

In a large bowl, beat the softened butter and granulated sugar together until light and fluffy, about 2-3 minutes.

Add the egg and vanilla extract to the butter mixture and mix until well combined.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Using a cookie scoop or tablespoon, portion out the dough and roll into balls.

Roll each ball in the powdered sugar until fully coated.

Place the dough balls on the prepared baking sheets, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers are still soft.

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