Here is a great recipe for someone who already knows how to make Swiss meringue buttercream, and is looking to branch out with a bold new flavour. If you have discovered the perfect method for your kitchen, skip the steps and just reference the ingredients for a silky, luxurious batch of dark chocolate frosting.
This icing is my go-to for chocolate celebration cakes because it is incredibly smooth, not too sweet, pipes beautifully, and freezes well. I developed this recipe using chocolate with 72% cocoa for a decisively dark taste with just the right amount of bitter-sweetness. The process begins with a brown sugar meringue, into which two cups of butter is emulsified. To finish, 300 grams of chocolate is melted, cooled to room temperature, and stirred into the caramel flavoured buttercream. The result is rich and creamy, yet light and fluffy, and perfect for smothering over layers of cake.
Chocolate Swiss Meringue Buttercream
Special Equipment: Stand mixer, digital candy thermometer.
7 large egg whites, approximately 215 grams
350 grams golden yellow or light brown sugar
1 lb unsalted butter, cubed
1/8 teaspoon table salt
1 1/2 teaspoons pure vanilla extract
300 grams extra dark chocolate (72% cocoa)
Remove the cold butter from the fridge, and cut it into tablespoon-sized chunks. Let the butter sit on the counter while you prepare the other ingredients. When the butter warms to 65° F, at which point it reaches the “plastic” stage, it will be just the right temperature and consistency to incorporate into the meringue. The butter is ready when you can push on a piece with your finger and it resists briefly before making a smooth indent. If the butter cracks at the pressure, it is too cold. If the butter offers no resistance or is very soft and greasy, it has become too warm and will melt into the meringue. Refrigeration is your friend in this case, do not hesitate to put the butter back into the fridge if it becomes too warm.
Separate the eggs, using clean bowls and making sure that no yolk or grease makes its way into the egg whites. It is a good idea to wipe all the bowls and tools that you plan to use clean with a paper towel and some fresh lemon juice, to eliminate any traces of grease which can prevent the meringue from reaching its full potential. Set up your mixer with a clean mixing bowl and the whisk attachment.
In a large metal bowl, whisk together the egg whites and sugar to combine. Create a double boiler by filling a large saucepan with a few inches of water, placing it on a burner set to medium-low heat, and fitting the metal bowl on top of the pot. Whisk the mixture very gently, frequently at first but constantly as the heat increases, just until it reaches 160° F on a candy thermometer.
Immediately pour the hot liquid into the bowl of your stand mixer, using the whisk to scrape in as much as possible. Gradually turn the mixer up to high (speed 6 on a KitchenAid) and beat for 7 minutes, or until the meringue is very stiff. Turn the speed down to low and beat for approximately 8 more minutes, or until the bowl is neutral to the touch. The meringue must be cool when the butter is added or it will melt on contact.
Quickly switch over to the paddle attachment, and with the mixer on low speed add the butter one piece at a time, waiting 10 seconds in between additions to ensure that each piece is fully incorporated. If after adding 3/4 of the butter the mixture appears very loose or soupy, place the bowl in the fridge for 7 to 10 minutes to bring down the temperature, then continue beating and adding butter. If the mixture becomes too cold at any point it will appear curdled, but keep beating on low and the buttercream will eventually smooth itself out. Take any pause in the process as an opportunity to scrape the bottom and sides of the bowl to ensure that all of the meringue is incorporated.
The frosting will come together and fluff up shortly after all of the butter is incorporated. When the buttercream is fluffy and smooth, beat in the salt and vanilla extract.
Melt the chocolate in a microwave or over a double-boiler, and let it cool to room temperature. The chocolate should be liquid, but if it is still warm when added to the bowl it will melt the butter.
Beat the buttercream for 30 seconds or until smooth, then unhook the bowl and add the melted chocolate. Fold in the chocolate with a rubber spatula for the darkest result. When the frosting is uniform in colour, it is ready for piping, swooshing, or swirling.