In a mixing bowl, whisk together granulated sugar, brown sugar, and melted butter until well combined.
Add the eggs one at a time, whisking well after each addition. Stir in the vanilla extract.
In another bowl, sift together the all-purpose flour, cocoa powder, baking powder, salt, and baking soda.
Gradually add the dry ingredients to the wet mixture, stirring with a rubber spatula until just combined. The dough will be thick and sticky.
Cover the bowl with plastic wrap and refrigerate for at least 2 hours, or overnight for best results.
Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
Using a tablespoon or cookie scoop, portion out the dough and roll it into balls. Roll each ball in powdered sugar until generously coated.
Place the coated cookie dough balls on the prepared baking sheet, 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 sheet for 5 minutes before transferring them to a wire rack to cool completely.