Preheat oven to 170°C. Line 12 cup muffin pan with paper cases.
In a bowl, sift flour, cocoa powder and bi-carb soda and baking powder. Mix in the sugar. In another bowl whisk together the buttermilk, butter, eggs, vinegar and vanilla until combined. Make a well in the centre of the flour mixture. Add the buttermilk mixture. Stir until just combined. Stir in the food colouring.
Bake for 20-25 minutes until a skewer comes out clean. Transfer to a wire rack to cool completely.
Use an electric beater to beat together the cream cheese, butter, icing sugar and vanilla until smooth. Spread or pipe over cupcakes.