- 3 large (90ml) egg whites
- 3/4 cup (150g) sugar
- 300g butter, softened
- 1 tsp pure vanilla extract food colouring, as desired
Place egg whites and sugar in a big metal bowl set over a saucepan quarter-full of gently simmering water. Make sure no steam or water gets into the egg whites, as this can keep them from whipping up properly. Immediately whisk gently by hand over the heat until sugar dissolves (test by rubbing a little mixture between your fingers - you should not feel any sugar granules).
Remove from the heat. Now change to an electric stand mixer fitted with a whisk attachment. Whip until the mixture cools, forms stiff peaks, turns white and doubles in volume (this will take at least 5 minutes).
Whisk in vanilla extract. Now add the butter in four additions (a quarter at a time) and continue to whisk after each addition. The mixture may appear almost curdled looking at first - be aware that this is normal. Keep whisking and it will become even and smooth.
Add food colouring, if required, and whisk to combine. Spread or pipe onto cupcakes and decorate, as desired.
Note - This buttercream does not get a crust on the surface and it stays fluffy even after sitting overnight (i.e. it does not deflate).