Preheat oven to 200•C. Paper-line 12 x 1/3 muffin cups.
In a medium bowl, mix sugar and egg whites together until smooth. In another bowl (a large one), beat butter and egg whites until light and fluffy.
Transfer sugar and egg white mixture into a butter mix, then mix until combined. Add in vanilla and beat well. Add in the milk, beat for about a minute until smooth.
Finally, add in sifted flour afterwards, then stir the batter until thick!
Using an ice-cream scoop-spoon, scoop the batter into prepared muffin cups. Bake for 25 to 30 minutes or until a tester inserted into the centre of one of the cupcakes comes out clean. Cool in a wire rack for about 10 minutes.
Using an electric mixer (and to make icing), beat butter in a bowl until pale. Gradually add icing sugar mixture and milk, beating constantly until combined. Beat in pink food colouring, if using, until combined. (If the icing starts to get runny, thicken it with a little more icing sugar!).
Spread/pipe the cupcakes with icing, then optionally decorated with anything you want!