Combine flour and cocoa powder in a bowl and set aside. Preheat oven to 350º F. Line the cupcake pans with liners and lightly spray them with cooking spray. Using the paddle attachment of your electric mixer, on medium speed, beat together butter and sugar until smooth.
Once smooth add oil and vanilla essence and mix again. Add milk and vinegar to the mixture. And now add the food coloring and keep mixing until it is combined together.
At this time add the flour mixture and let the mixer run until combined. Do not over mix the batter. Divide batter evenly among liners a little bit more than half. Bake for 18 - 20 minutes or until a toothpick inserted into the center comes out clean.
Let it rest for 5 minutes in the pan then turn out onto a cooling rack and allow to cool completely before frosting.
Whip the cool whip with the castor sugar until its slightly stiff. Place the star tip and fill the pastry bag with the cream to decorate. I have decorated the cupcakes with rosettes, you can decorate as you like.