Preheat your oven to 175C / 350F. Line two baking trays with baking paper and set aside. Add the cocoa powder, white sugar, melted butter and vegetable oil into a large mixing bowl and use a whisk to mix until well combined. Then add the egg and mix until well combined.
Add the flour, baking powder, salt and half the chopped chocolate and use a spatula to mix until a dough forms.
Use a large ice cream scoop to scoop 12 cookie balls. Squish them in your hand and roll into a ball. Then squash them down between the palms of your hand. Place on the baking trays and bake for 10 minutes.
Once baked, add more chopped chocolate on top. Use a large round cookie cutter to shuffle around to get into rounder shapes. Allow to cool before serving.