The oven must be put on Preheat to 175°C. Arrange 2 baking trays or cookie sheets with baking paper.
Take a bowl of medium size and really mix the cocoa powder well with white sugar, vegetable oil and butter. Until the mixture settles well, beat in the egg and vanilla.
Put the flour, salt and baking powder, and primarily stir the dry ingredients prior to combining them with the wet ingredients till the dough settles (be careful to not overbeat).
Take 1-2 scoops of dough with a cookie scoop and add them to the set baking sheets. As per your gut feeling, design them as thick or thin for your cookies to look.
Finally, bake in a hot preheated oven for about 10-12 minutes. The cookies will be delivered in the way you want.