Why It Works
- Sugar improves the volume of the meringue, for a light and creamy frosting.
- Toasted sugar or brown sugar adds complexity with subtle notes of caramel or molasses, respectively.
- Cream of tartar is acidic, adding a counterpoint to the meringue's sweetness.
- At 185°F (85°C), the egg white syrup will be fully cooked.
- Dark chocolate stands up to dilution in sugar and butter, whether the goal is a milk- or a dark-chocolate profile.
- Subtle use of espresso powder can provide more depth of flavor to the chocolate.
If you need to whip up a chocolate frosting on the fly, but don't want to compromise on flavor or texture, Swiss buttercream is the way to go. It's a favorite among professional bakers because it's fast and easy to prepare, super stable for decorating purposes, and way smoother and airier than frostings based on powdered sugar. And, let's cut to the chase, it tastes incredible—like a creamy chocolate mousse crossed with brownie batter, all buttery and rich.
I've written extensively about both Swiss meringue and Swiss buttercream, so I won't go into a ton of detail here other than to say that my Swiss meringue is fully cooked, and significantly lighter and more stable than recipes you may have tried before. That's because I favor a cooking style that uses more sugar and a higher cooking temperature.
This combination produces a meringue, and in turn a buttercream, that's unusually sturdy and not at all heavy—it weighs in at just six ounces per cup. In the case of buttercream, the meringue's high sugar content dilutes the richness of the butter, for a frosting that feels light rather than greasy.
I take the same overall approach when making a chocolate buttercream, but with a few key tweaks. Instead of plain white sugar, I start with toasted sugar, Belgian cassonade (also called candi sugar), or light brown sugar. These super-flavorful sugars add a hint of caramel or, in the case of light brown sugar, molasses, which tames the sweetness of the meringue, provides deeper flavor, and complements the earthy chocolate. It's a simple way to build more flavor into the recipe from the ground up.
Whether you opt for a caramel- or a molasses-based sugar, the key is to cook the meringue over the water bath until it hits 185°F (85°C) to ensure it's fully cooked despite the high sugar content, and to denature the egg whites to improve their volume as a meringue.
Transfer the bowl to a stand mixer, and whip on high until the meringue is thick, fluffy, and cooled to about 90°F (32°C). Since that's lower than body temperature, the bowl will feel cool to the touch, but it's warm enough to accommodate the addition of cool butter—aim for butter that's about 65°F (18°C).
Together, the cool butter and warm meringue will average out to about 72°F (22°C), the ideal working temperature for a classic Swiss meringue buttercream. Bear in mind that there are countless temperature combinations that will bring you to that target. In my pastry days, I'd routinely use hot meringue and butter straight from the fridge, but for beginners, it's easiest to take a path that avoids such extremes.
Should circumstance push the buttercream toward the warm or cool end of the spectrum, it will range from soft and soupy to stiff and curdled. Fortunately, these issues are never bad enough to ruin the buttercream, and they're easy to fix if you consult my Swiss buttercream troubleshooting guide. Problems related to temperature will only compound if they’re not addressed along the way, so it’s essential that you make sure the buttercream is at a good working temperature before trying to incorporate a temperature-sensitive ingredient like chocolate. Plus, a cold buttercream may cause the chocolate to harden against the edge of the bowl, while warm buttercream won't have enough structure to withstand the addition of warm chocolate.
On that note, whether you want the frosting to have a dark- or milk-chocolate flavor, it's important to start with dark chocolate. That's because even if you use a half pound of dark chocolate, the sugar and fat inherent to buttercream will instantly dilute its flavor, making it taste like milk chocolate from the get-go. Actually getting a dark-chocolate flavor takes nearly twice as much chocolate. For that reason, milk chocolate itself is useless: too mellow and mild to overcome the sheer quantity of sugar and butter involved.
I recommend using a dark chocolate with cocoa solids of somewhere between 72 and 77%. (For this frosting, I used Chocolove 77% because it's always on sale at my local supermarket, but it's also very affordable when purchased in bulk online.) At lower percentages, the chocolate will contain more sugar and less chocolate, making it a poor flavoring agent. At higher percentages, the increase in cocoa butter can create a buttercream that seems stiff and greasy due to its high melting point (around 95°F/35°C).
However much melted chocolate you decide to add, it should be cooled to about 80°F (27°C) and poured into the buttercream all at once. Immediately start whipping on medium-high to incorporate the chocolate; once it looks relatively well combined, pause and scrape the bowl to be sure that there's no chocolate clinging to the sides, where it can solidify into pesky chips. After scraping, continue whipping until the buttercream looks creamy and smooth.
When you're combining warm chocolate and buttercream, it's not unusual for the temperature to skew high, which can make the buttercream a little soft and soupy. Per my troubleshooting guide, the answer is simple: Pop the buttercream into the fridge for 10 minutes, then whip on medium-high for about five minutes to homogenize its temperature and texture. Afterward, it should be smooth, thick, and wonderfully light.
From there, the chocolate buttercream can be doctored with added salt or vanilla to taste; when aiming for a dark-chocolate flavor, I like to add a small amount of dissolved espresso powder for a little extra depth. Once you've dialed in the flavor, the buttercream is ready to spread over your favorite layer cake, whether that's a classic vanilla butter cake or a fluffy strawberry torte. For more information on assembly, check out this tutorial on how to crumb-coat a cake.
Cakes frosted with Swiss buttercream don't require refrigeration, though it's a helpful step to prepare the cake for long-term storage or transportation. If you do refrigerate the cake, remember that cold buttercream feels greasy and hard on the tongue, and that's doubly true of chocolate buttercream. For any layer cake that's spent some time in the fridge, always budget plenty of time for the cake to return to room temperature before serving.
6 ounces egg whites (2/3 cup; 170g), from 5 to 6 large eggs
11 ounces toasted sugar, Belgian cassonade, or light brown sugar (about 1 2/3 cups; 310g); see notes
1 teaspoon (4g) Diamond Crystal kosher salt (plus more if needed); for iodized salt, use half as much by volume or the same weight
1/4 teaspoon cream of tartar
16 ounces unsalted butter (4 sticks; 455g), softened to about 65°F (18°C)
1 teaspoon (5g) vanilla extract (plus more if needed)
8 to 14 ounces finely chopped dark chocolate, between 70 and 77% cocoa solids (about 1 1/3 to 2 1/3 cups; 225 to 395g)
1 teaspoon instant espresso powder (optional), dissolved in a few drops of hot water
Fill a wide pot with at least 1 1/2 inches water, with a thick ring of crumpled tinfoil placed on the bottom to act as a "booster seat" that will prevent the bowl from touching the bottom of the pot. Place over high heat until steaming-hot, then adjust temperature to maintain a gentle simmer. Combine egg whites, sugar, salt, and cream of tartar in the bowl of a stand mixer. Set over steaming water, stirring and scraping constantly with a flexible spatula, until egg whites hold steady at 185°F (85°C). This should take only 10 to 12 minutes, so if the mixture seems to be moving slowly, simply turn up the heat. Once ready, transfer to a stand mixer fitted with a whisk attachment and whip at high speed for about 10 minutes, until meringue is glossy, stiff, and cool to the touch, around 90°F (32°C).
With mixer still running, add butter, 1 or 2 tablespoons at a time. Initially, the volume of the meringue will decrease dramatically; it may even seem soupy along the way, but as the cool butter is added, the mixture will begin to thicken and cool. In the end, the buttercream should be thick, creamy, and soft but not runny, around 72°F (22°C). Mix in vanilla extract on low speed until well combined.
Melt chocolate, either in a microwave or over a water bath, until fluid and warm; start at the lower end of the suggested quantity range for a "milk" chocolate profile, or use the maximum amount for the deepest chocolate flavor. Scrape all of the warm chocolate into stand mixer bowl at once, then immediately begin whipping on medium-high until fully incorporated. Scrape bowl with a flexible spatula to ensure there is no unincorporated chocolate lurking around sides of bowl, then continue mixing until homogeneous. If you like, adjust to taste with additional salt, vanilla, or dissolved espresso powder to add depth of flavor.
Use buttercream right away, or transfer to a large zipper-lock bag, press out air, and seal. Buttercream can be refrigerated for up to 2 weeks and frozen for up to several months. (The main issue with longer storage in the freezer is odor absorption, not spoilage.) Rewarm to approximately 73°F (23°C) and re-whip before using.
Troubleshooting: If warmer than 76°F (24°C), the buttercream will be soft and loose; pop it in the fridge for 15 minutes and re-whip to help it thicken and cool. If colder than 70°F (21°C), the buttercream will be firm and dense, making it difficult to spread over cakes and slow to melt on the tongue, creating a greasy mouthfeel. To warm, briefly set over a pan of steaming water, just until you see the edges melting slightly, then re-whip to homogenize. Full troubleshooting guide and video here.
Sugars with a caramel flavor, such as quick- or slow-roasted sugar, or even Belgian cassonade (candi) sugar, tame the sweetness of meringue while underscoring the chocolate with a rich, toasty note. Molasses-based alternatives, such as turbinado, Demerara, or American-style light brown sugar, work well, too, but will give the buttercream a tangier profile overall.
Make Ahead and Storage
Buttercream can be refrigerated for up to 2 weeks and frozen for up to several months. (The main issue with longer storage in the freezer is odor absorption, not spoilage.) Rewarm to approximately 73°F (23°C) and re-whip before using.
|Nutrition Facts (per serving)|
|Amount per serving|
|% Daily Value*|
|Total Fat 9g||12%|
|Saturated Fat 6g||28%|
|Total Carbohydrate 9g||3%|
|Dietary Fiber 0g||1%|
|Total Sugars 9g|
|Vitamin C 0mg||0%|
|*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.|