Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a bowl, whisk together the flour, cocoa powder, baking powder, and salt.
In another bowl, mix the granulated sugar, brown sugar, and vegetable oil until well combined.
Add the egg and vanilla extract to the sugar mixture, and mix until smooth.
Gradually incorporate the dry ingredients into the wet mixture, stirring until just combined.
Chill the dough in the refrigerator for about 30 minutes.
Use a cookie scoop to portion out the dough and roll each portion into a ball.
Roll the dough balls in powdered sugar, ensuring they are well coated.
Place the coated dough balls onto 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 a few minutes before transferring them to a wire rack.