Preheat your oven to 350°F (175°C) and line a baking tray with parchment paper or a silicone baking mat. Sift together the flour, cocoa powder, baking powder, and salt in a medium bowl. Set aside.

Using a hand mixer or stand mixer, cream the softened butter, granulated sugar, and light brown sugar together until light and fluffy (2-3 minutes). Beat in the egg and vanilla extract until well combined.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until the dough comes together. If you're adding chocolate chips or nuts, gently fold them in at this stage.

Cover the bowl with plastic wrap and place it in the refrigerator for 30 minutes (or the freezer for 15 minutes). This helps the dough firm up for easier handling.

Use a cookie scoop or tablespoon to scoop the dough, then roll it into balls (about 1 inch in diameter). Roll each ball in powdered sugar until fully coated and place them on the prepared baking tray, about 2 inches apart. Bake for 10-12 minutes until the cookies are set but still soft in the center.

Remove the tray from the oven and let the cookies cool on the tray for 5 minutes before transferring them to a wire rack. Enjoy warm or store for later.