The recipe comes from wedding cake genius and my unpaid assistant, Torrie.
For a wedding cake (or most of one, depending on the size)
2 cups of egg whites (approx. 12 large)
3 cups sugar
5 cups butter, softened (2 1/2 pounds, 10 sticks)
1 tablespoon vanilla extract
For a 9-inch cake (plus filling, or some to spare)
1 cup sugar
4 large egg whites
26 tablespoons butter, softened (3 sticks plus 2 tablespoons)
1 teaspoon vanilla extract
For the tiniest amount, if you’re just practicing (or enough to cover and fill the 4-inch cake pictured)
1/4 cup sugar
1 large egg white
6 tablespoons butter, softened
1/4 teaspoon vanilla
Whisk egg whites and sugar together in a big metal bowl over a pot of simmering water. Whisk occasionally until you can’t feel the sugar granules when you rub the mixture between your fingers.
Transfer mixture into the mixer and whip until it turns white and about doubles in size. (Here’s a tip: when you transfer to the mixer, make sure you wipe the condensation off the bottom of the bowl so that no water gets into the egg whites. This can keep them from whipping up properly.)
Add the vanilla.
Finally, add the butter a stick at a time and whip, whip, whip.
Deb note: Do not have a panic attack when this takes a while to come together (though I did every time). One super-large batch took 15 minutes, but it did and will come together. Patience, young Jedis.