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

Beat in the eggs one at a time, then stir in the vanilla extract.

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

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. The dough will be soft.

Cover the dough and chill in the refrigerator for at least 1 hour, or until firm enough to roll into balls.

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

Place the powdered sugar in a shallow bowl. Roll tablespoonfuls of chilled dough into balls.

Roll each dough ball in the powdered sugar, ensuring it's fully coated.

Place the coated dough balls about 2 inches apart on the prepared baking sheets.

Bake for 9-12 minutes, or until the edges are set but the centers are still slightly soft.

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