Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large mixing bowl, combine the granulated sugar, brown sugar, and softened butter. Beat together until creamy.
Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.
In another bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until well combined. The dough will be thick and slightly sticky.
Chill the dough in the refrigerator for about 30 minutes for easier handling.
Once chilled, use a spoon to scoop out portions of dough (about 1 tablespoon each). Roll each portion into a ball.
Roll each ball in powdered sugar until thoroughly coated, then place them on the prepared baking sheet about 2 inches apart.
Bake for 8-10 minutes, or until the cookies are set and have crinkled on the surface. They should still look slightly soft in the middle.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.