Pre-heat a fan forced oven to 180°C.
Line a muffin tray with 12 cases.
Sift flour, baking powder, corn starch, cocoa and salt together. Whisk to ensure everything is mixed.
In another bowl, beat the butter for 1 minute. Add the sugar and beat until creamed together (approximately 2 minutes). Add the oil, egg yolks, vanilla extract and food colouring.
Fold 1/3 of the flour mixture and 1/3 of the buttermilk into the butter mixture. Continue this process until the flour and buttermilk has been incorporated.
Whisk the egg whites until soft, white peaks form. This will approximately take 2 - 3 minutes.
Fold the egg whites into the butter / flour mixture. Do not over mix.
Spoon the batter into the muffin cases. Bake for approximately 20 minutes or until a skewer comes out clean after pricking a red velvet cupcake.
Transfer to a wire rack and allow to cool before frosting (as residue heat can melt the frosting).