Preheat the oven to 180°C/350°F/Gas 4
Add the butter into a bowl and beat until soft and fluffy.
Add the sugar, flour, salt, eggs and milk and whisk for about five minutes until the mixture is pale and fluffy.
Use a ice-cream scoop, or spoon, to divide the mixture between all the paper cases.
Place the tins in the oven and bake for 18-20 minutes until pale golden in colour.
Take out of the oven and leave to cool in tins for a few minutes and then transfer to wire rack to cool further before icing.
Leave the cupcakes to cool in the tins for a few minutes, then transfer them to a wire rack to cool.
For the buttercream icing: Beat the butter in a bowl and then add half the icing sugar and beat until the mixture is smooth.
Add the rest of the icing sugar,a few drops of the food colouring, one tablespoon of the milk,more if necessary until the icing is smooth and creamy.
Spoon the icing onto the top of the cupcake and decorate with sprinkles.