This website has different recipe sizes for different size cakes.
The recipe I show in the video is the following: 1/2 cup sugar 2 large egg whites 3/4 cup butter softened 1/2 tsp vanilla extract
It was enough to generously frost about 6-8 cupcakes (depending on the cupcake size).
Place a big metal bowl over a pot of simmering water. Immediately add the sugar followed by the egg whites. Whisk together over the simmering water until you can't feel the sugar grains when you rub the mixture between your fingers.
Transfer mixture into a stand mixer if desired or leave it in the bowl and and whip with an electric hand mixer until it turns white and about doubles in volume.
Blend in the vanilla.
Add the butter in about 3 additions or so and continue to whip until the mixture gets thick and you think that it is thick enough to decorate with.
This buttercream does not get a crust on the surface and it stays fluffy even after sitting overnight (does not flatten). Because of the egg whites, you would need to refrigerate the decorated cakes/cupcakes after they are frosted.
This frosting is light, creamy and wonderful. It is not sickly sweet like some other buttercream frosting and I will be using this one for future projects.
I have no idea why this is called "Swiss" buttercream and I'm sure I will hear about how they don't make this frosting this way in Switzerland.