Preheat oven to 180°C (160°C fan forced). Line a 12 hole ⅓ cup capacity Wiltshire muffin tin with cupcake papers.
Place the flour, butter, sugar, eggs, milk and vanilla essence in the bowl of an electric mixer. Starting off on a low speed and increasing to high, beat ingredients together for 2 minutes or until pale and creamy. Divide mixture between the prepared papers. Bake for 15-20 minutes or until cupcakes spring back when lightly touched. Allow to stand for 5 minutes before transferring to a wire rack to cool completely.
To make the buttercream icing, place the butter in the bowl of an electric mixer and beat for 5 minutes or until pale and creamy. Gradually add the icing sugar, beating as you go. Add the milk and vanilla essence beating well to combine.
Place the icing in a piping bag fitted with a 2cm star nozzle and pipe a swirl of icing onto each of the cooled cupcakes. Decorate as desired.