Begin by preheating your oven to 350°F (175°C). Prepare a baking sheet by lining it with parchment paper to prevent sticking.
In a large mixing bowl, carefully combine the all-purpose flour, unsweetened cocoa powder, granulated sugar, packed brown sugar, baking powder, baking soda, and salt. Stir well with a whisk or spoon, breaking up any lumps to ensure a smooth mixture.
Form a well in the center of the dry ingredients. Into this well, pour the vegetable oil followed by the two large eggs and the vanilla extract.
Using a whisk or a sturdy wooden spoon, mix the ingredients together until just combined. The mixture will be thick and somewhat sticky, forming a rich batter.
For better handling, place the bowl in the refrigerator and chill the cookie dough for approximately 30 minutes. This step helps firm up the dough, making it easier to shape.
After chilling, take a spoon or a cookie scoop and portion out the dough, aiming for about 1 tablespoon per cookie. Roll each portion into a ball between the palms of your hands.
Generously roll each dough ball in powdered sugar, coating them thoroughly. Arrange the coated balls on the prepared baking sheet, leaving about 2 inches of space between each to allow for spreading.
Place the baking sheet in the preheated oven and bake for 10-12 minutes, or until the cookies have puffed and developed set edges while remaining soft in the center.
Once baked, remove the cookies from the oven and let them cool on the baking sheet for about 5 minutes. After that, carefully transfer them to a wire rack to cool completely.
Notes
To add a festive flair, arrange the cookies on a decorative platter. For an extra touch, dust with a light layer of powdered sugar just before serving.