Preheat the oven to 180℃ (356 Fahrenheit). Combine the cake flour, cocoa, and sugar in a bowl with a whisk. The cocoa will get lumpy, so sift it.

Once the dry ingredients have been mixed, add the vegetable oil. Add the vanilla oil as well.

Use a rubber spatula to mix it up. It's okay if it becomes crumbly.

Wrap the crumbly dough in plastic wrap.

Shape the dough into a clump with your hands over the wrap.

Once the dough is all together, remove the wrap.

Roll the dough into bite-sized pieces (about 10 g each). Arrange on parchment paper-lined baking sheet and bake at 180℃ (356 Fahrenheit) for about 15 minutes.

Once baked, they will break easily, so let cool on the baking sheet. Once cooled, sprinkle as you like with powdered sugar.

These are the cookies I made.

These are dusted with powdered sugar, but it's fine to leave your cookies uncoated too.