this recipe is for your basic swiss buttercream, which is a little bit more work than the classic butter + sugar + flavor buttercream, but well worth the effort. its so light and dreamy, it made little ol me — who usually can take or leave frosting — a frosting fan. it’s great for wedding cakes.
i made this last year for a daring bakers challenge (doesn’t it look good with the cake?) and i’ve been comparing every frosting to it ever since.
if you’re scared of curdling, it can be frightening the first time, but don’t be scared. just do it. you’ll thank me later.
(the recipe below, borrowed from dorie greenspan, is for a lemon buttercream, but flavoring can be adjusted at your whim.)
the best buttercream ever.
1 cup sugar
4 large egg whites
3 sticks (12 ounces) unsalted butter, at room temperature
¼ cup fresh lemon juice (from 2 large lemons)
1 teaspoon pure vanilla extract
put the sugar and egg whites in a mixer bowl or another large heatproof bowl, fit the bowl over a pan of simmering water and whisk constantly, keeping the mixture over the heat, until it feels hot to the touch, about 3 minutes. the sugar should be dissolved, and the mixture will look like shiny marshmallow cream. remove the bowl from the heat.
working with the whisk attachment or with a hand mixer, beat the meringue on medium speed until it is cool, about 5 minutes. switch to the paddle attachment if you have one, and add the butter a stick at a time, beating until smooth.
once all the butter is in, beat in the buttercream on medium-high speed until it is thick and very smooth, 6-10 minutes. during this time, the buttercream may curdle or separate –- just keep beating and it will come together again.
on medium speed, gradually beat in the lemon juice, waiting until each addition is absorbed before adding more, and then the vanilla. you should have a shiny smooth, velvety, pristine white buttercream.
press a piece of plastic against the surface of the buttercream and set aside briefly.