• 12 large egg whites (14 oz by weight)
• 1 pound 4 oz granulated sugar
• 2 pounds butter, softened, cut into tablespoon-sized pats
• Vanilla extract, to taste (or flavored extract or liqueur of your choice)

1. In a mixing bowl set over simmering water, whisk egg whites and sugar until sugar dissolves.
2. Place mixing bowl in a stand mixer, and using wire whip, whip the whites on medium-high speed to stiff peaks (about 10 minutes).
3. Switch to paddle attachment. Add butter, one or two pats at a time, beating after each addition until fully incorporated. Full incorporation will take longer as more butter is added.
4. Do not be alarmed if buttercream looks "curdled," it will smooth out with continued beating.
5. After the butter is added, mix in vanilla and continue beating until combined.

During pastry school, we made a batch of each variety of buttercream: Italian, French, Swiss and American. I preferred Swiss by far, and it's the only buttercream I use. It's smooth, not overly sweet, nor overly buttery. The following recipe should frost and fill one 9-inch layer cake.