Preheat your oven to 180 Fan / 200 C / 400 F / Gas 6 and put 12 large cupcake (or muffin) cases into your muffin tin.
Put the milk into a small bowl or jug, whisk in the vinegar and set aside while you weigh the remaining ingredients.
In a large bowl put the sugar, flour, baking powder and bicarbonate of soda and stir together.
Whisk the oil and whisky into the milk then pour into the bowl of dry ingredients. Use a large whisk or rubber spatula to mix everything together. Mix until it's all just combined, try not to over-mix.
Divide the mixture equally between the muffin cases then bake for 20-25 minutes until springy to the touch or a toothpick inserted into the centre of one of the cupcakes comes out clean with no raw cake mix clinging to it.
Cool in the tin for 5 minutes before transferring to a cooling rack to cool completely.
While the cupcakes are cooling make the frosting - beat the butter until it's pale and creamy. I use a stand mixer but you can use an electric whisk if you soften the butter first. Then beat in the icing sugar and a little milk to make a fluffy buttercream
Add 20 drops of the cola flavouring and beat in then taste. Add a few drops more if you think it needs to be a little stronger in flavour.
Spoon into a piping bag fitted with a star nozzle and set aside until the cupcakes are cooled.
Once the cupcakes are completely cool pipe on the frosting in fluffy swirls and devour in lip licking satisfaction!