In a large bowl with an electric mixer, beat the butter until light and fluffy; about 2-3 minutes. Add sugars and beat again until light and fluffy; about 4-5 minutes.
Stir in the cocoa powder until smooth.
Stir in the the eggs until well incorporated.
In a separate medium bowl, whisk together the flour, baking powder and salt. Stir into the wet ingredients just until combined, then cover and refrigerate for 20 minutes.
Once chilled, preheat the oven to 350 degrees Fahrenheit and prepare a baking sheet with parchment paper silicone mats and set aside.
Using a cookie scoop or your hands form 1-inch cookie balls and roll them around in the powdered sugar. Place 2-inches apart evenly on the prepared baking sheet.
Bake for 9-11 minutes, or until the tops have cracked and the dark brown parts only look slightly wet (they will still jiggle, but once cooled they will firm up). Let cool for 5 minutes on the pan and then remove them and let them cool on a cookie cooling rack for 5 more minutes.
These cookies are best enjoyed fresh, but can be stored in an airtight container for up to 5 days.