Chocolate Swiss meringue buttercream is a stable frosting that is not too sweet. And it’s a light chocolate meringue frosting to make.
⅔ cup of sugar
4 large egg whites
¼ teaspoon salt
1 ½ cups unsalted butter, cut into pieces, softened – SEE NOTE 1
10 ounces semisweet chocolate, melted and cooled – SEE NOTE 2
1 teaspoon vanilla extract
Combine sugar, egg whites, and salt in the bowl with a stand mixer. Place the bowl over a saucepan filled with 1 inch of barely boiling water. Whisk gently and continuously while heating the frosting. It should detect 150 ° F on an instantaneous thermometer. The sugar must be fully dissolved.
Transfer the bowl to the stand mixer and mount it with the whisk. Whisk on medium speed until mixture is consistent with shaving cream and cooled slightly 1-2 minutes. (If the meringue is hot, it melts the butter.)
Gradually add the butter, 1 tbsp at a time, until smooth and creamy. (Only add the next tablespoon of butter when the previous one has been completely mixed in.)
When all the butter has been added, scrape down the sides of the bowl and mix on medium-high and beat until light and fluffy, approx. 30 seconds.
Add the cooled, melted chocolate and vanilla. Mix on medium speed until combined. Turn the speed up to medium-high and beat until light and airy, approx. 30 seconds.
The butter must be softened to approx. 60 ° F. It should be soft enough to press an indentation with the fingertip, but not so soft that it is greasy or melting. Butter that’s too soft will turn the frosting into a soup.
Use high-quality baking chocolate in bar form. Avoid using chocolate chips, melting waffles, or any kind of composite chocolate. They simply do not work with this recipe.
You can use semi-sweet, milk, dark, bittersweet, or white chocolate, as long as it is real chocolate in bar form.
Do not start adding the butter until the meringue has cooled completely! If the meringue is hot, it melts the butter and turns the frosting into a soup.
If your frosting curls and does not smooth out with 5 minutes of mixing, do not panic. You can save it by heating the side of the bowl with a hairdryer while the mixer is running. Do this until the frosting starts to come together, turn off the hairdryer, and keep beating until the frosting is light and airy. Or you can place it at approx. ⅓ cup curd in a microwave-safe bowl and microwave for approx. 15-30 seconds. Give it an honest whisk, then add it back to the most bowl of frosting. Whisk on medium speed until the frosting comes together.
If your frosting is loose and souped, it can be saved by placing the bowl and whipped cream in the fridge for approx. 20 minutes. Then pop the frosting until it is light and fluffy.
Do not add the melted chocolate until it has cooled to the touch. Hot chocolate can cause the buttercream to clump or loosen too much.