Romantic Red Heart Cakes

For the cupcakes: heat the oven to 160°C (140° fan) 325°F gas 3. Place paper cases in a 12-hole bun tin.

Sift the flour, cocoa, bicarbonate of soda and salt into a bowl.

In another bowl mix the buttermilk, vinegar, vanilla and red food colouring.

Beat the butter and sugar in a mixing bowl until pale and fluffy. Beat in the egg a little at a time. Mix in 1/3 of the flour mixture, followed by half the buttermilk mixture, then another third of the flour, the remaining buttermilk and finally the last of the flour mixture.

Spoon into the paper cases. Bake for about 20 minutes, until risen and springy to the touch. Cool in the tin for 5 minutes, then place on a wire rack to cool completely.

For the topping: whisk all the ingredients together in a food processor or with an electric whisk until smooth. Cover and chill for 1 hour before using.

Spread the topping over the cakes.

To decorate: stir together the sugar and red food colouring, until the sugar is evenly coloured.