Swiss Meringue Buttercream

This is Martha Stewart's Swiss Meringue Buttercream recipe. It makes a beautifully glossy and smooth frosting that isn't too sweet. I also like that the egg whites are heated, unlike French buttercream recipes that use uncooked egg whites. The recipe isn't hard, but you do have to follow the directions carefully, or you'll end up with a clumpy mess. I know because I've ended up with a clumpy mess! The recipe makes A LOT of frosting, so feel free to halve, or just throw the extra in the fridge or freezer. You'll need to beat it again before you use it.

I used this recipe for all the cakes in the photos.  Although the buttercream is very creamy and seems like it would melt in the slightest heat, if made correctly it actually holds up really well.  

Swiss Meringue Buttercream

• 1 1/2 cups sugar
• 6 large egg whites
• Pinch of salt
• 1/4 teaspoon cream of tartar
• 2 cups (4 sticks) unsalted butter, cut into tablespoons, room temperature
• 1 teaspoon pure vanilla extract

Heat sugar and eggs: Bring a saucepan filled with about 2 inches of water to a simmer. Meanwhile, combine sugar, egg whites, and salt in a large heat-proof mixing bowl. Set bowl over (not in) simmering water, and whisk frequently until whites are warm to the touch and sugar is dissolved, 8-10 minutes. (Heating the eggs relaxes their proteins, enabling the eggs to whip up higher and more quickly; the sugar also melts, for a silky smooth consistency.) Test by rubbing between your fingers; the mixture should feel smooth and not grainy.

Whip meringue: Attach the bowl to a standing electric mixer fitted with the whisk attachment, and beat on low speed until foamy. Add cream of tartar, and beat on medium-high speed until stiff, glossy peaks form and mixture is cooled completely, about 10 minutes.   Feel the bottom of the bowl to make sure it isn't warm.

Mix in butter: Reduce speed to medium-low; add butter 2 tablespoons at a time, beating to incorporate fully after each addition. Don't worry if the buttercream appears curdled at this point; it will become perfectly smooth again with continued beating. Keep the mixer at a low speed - high speeds will create a clumpy texture.  After all the butter has been incorporated, beat in vanilla.

Finish: Switch to the paddle attachment. Beat on the lowest speed to reduce air bubbles, 3 to 5 minutes. Let stand, covered with plastic wrap, at room temperature.

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