Why It Works
- A higher proportion of sugar serves to dilute the addition of butter down the road, for a frosting that never feels greasy.
- Toasted sugar brings the overall sweetness into balance, adding complexity of flavor.
- Cream of tartar is acidic, adding a counterpoint to frosting's simple sweetness.
- At 185°F (85°C), the egg white syrup will be fully cooked.
- An optional touch of almond extract rounds out the vanilla, giving the buttercream more depth of flavor.
- Testing the finished buttercream with a thermometer helps rule out problems related to temperature, a common concern in recipes built on butter.
Swiss meringue buttercream is the fastest and easiest frosting around, made from an ingredient so humble it's often just thrown away: leftover egg whites. They're cooked over a water bath, whipped into an airy meringue, then enriched with butter, for a silky-smooth frosting that tastes light and mild—a blank canvas waiting for your creative touch. Peanut butter? Melted chocolate? Vanilla beans? Ground peanut brittle? Freeze-dried fruit? Sure thing! Mix in whatever you like, and Swiss buttercream will make it the star.
One thing to note is that Swiss meringue is commonly made with too little sugar and not enough heat, producing something that's eggy, fragile, and raw. From there, adding butter only makes it greasy and dense, a frequent gripe among detractors of SMBC (as it's called online). If you joined me on my quest for the perfect meringue pie last year, you know that I've spent a not-insignificant amount of time tinkering with Swiss meringue to overcome those common complaints.
You can check out my full report here, but the short story is this: With a bit more sugar and a higher target temperature, Swiss meringue loses its eggy flavor and whips up stable, light, and fully cooked (the traditional advantages of an Italian meringue). If Swiss meringue starts with toasted sugar and vanilla bean, it can also be remarkably delicious.
It's a rock-solid foundation for buttercream as is, but a few extra tweaks make it all the more outstanding. Bumping up the sugar, salt, and vanilla in my Swiss meringue ensures that its flavor and sweetness aren't overpowered by the butter. In turn, the added sugar offsets the butter's richness, so the finished product feels lighter than recipes that call for less. That additional sugar does require the meringue to be cooked to a higher temperature, but aside from that adjustment, the technique stays the same.
If you haven't made a Swiss meringue before, the process is simple. Combine egg whites, toasted sugar, cream of tartar, salt, and vanilla seeds in a double boiler, and cook, stirring constantly with a flexible spatula. For this recipe, you'll take the mixture to about 185°F (85°C) to make sure it's fully cooked. Then you'll whip it on high speed until the meringue is fluffy, light, and cool to the touch, about 90°F (32°C).
Sure, 90°F doesn't sound cool, but it's well below body temperature, so the bowl won't feel warm against your palm. It's also the perfect temperature to accommodate the butter, which should be pliable and cool, about 65°F (18°C). Whipped together, they'll average out to about 72°F (22°C).
You can achieve that perfect temperature any number of ways, with a cooler meringue and warmer butter, or vice versa, but that's a tightrope beginners needn't walk. Though you have a few degrees of wiggle room in either direction, if the ingredient temperatures aren't properly balanced, the buttercream may be runny and thin, or dense and greasy—maybe even curdled and broken. With an awareness of the role temperature has to play, and a trusty digital thermometer, all those problems simply cease to exist. (If you're in the market for a thermometer, mine's a Polder. The clip-on attachment, heat-safe cord, and temperature alert make it ideal for a wide range of desserts, plus savory projects, too.)
Freshly made Swiss buttercream has the ideal consistency for frosting cakes and cupcakes, but it can also be kept in short- or long-term storage—a fact I rely on to polish off the egg whites left over from other baking projects. Simply roll open the mouth of a gallon-sized, heavy-duty zip-top bag; scrape in the buttercream; press out the air; and seal. It'll keep about two weeks in the fridge, or several months in the freezer. (The issue with freezing for longer than that isn't spoilage so much as odor absorption.) Do be sure to lay the bag flat, which helps the buttercream to thaw rapidly down the line. When you're ready to frost a cake, warm the buttercream back to 72°F, then re-whip to restore its spreadably soft consistency.
With toasted sugar, loads of vanilla, and a drop of almond extract, my Swiss meringue buttercream tastes more satisfying than traditional recipes, while remaining simple and familiar. It's my go-to vanilla frosting when time is of the essence, and a far silkier option than anything made with powdered sugar. It's also a great springboard for new flavors, whether you trade toasted sugar for molasses-y Demerara or spike the buttercream with a concentrated fruit purée.
Because it's fully cooked, cakes frosted with Swiss buttercream don't require additional refrigeration; the cake itself will stale faster than the buttercream can spoil. Whether other versions have let you down or you've never made it at all, I hope you'll give my Swiss buttercream a chance. And should the worst come to pass, don't worry: We've got a complete troubleshooting guide that'll put your frosting back on track, no matter the problem.
How to Make Swiss Buttercream Frosting
6 ounces egg whites (2/3 cup; 170g), from 5 to 6 large eggs
11 ounces plain or lightly toasted sugar (about 1 2/3 cups; 310g) (see notes)
3/4 teaspoon (3g) Diamond Crystal kosher salt; use half as much if iodized
1/4 teaspoon cream of tartar
Scraped seeds from 1 split vanilla bean (optional)
20 ounces unsalted butter (5 sticks; 565g), softened to about 65°F (18°C)
1 teaspoon (5ml) vanilla extract
1/4 teaspoon almond extract (optional)
Fill a wide pot with at least 1 1/2 inches of 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, cream of tartar, and vanilla seeds (if using) 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 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 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, buttercream should be thick, creamy, and soft but not runny, around 72°F (22°C). Mix in vanilla extract and almond extract (if using) on low speed until well combined.
Use buttercream right away, or transfer to a large zipper-lock bag, press out the 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 72°F and re-whip before using.
Troubleshooting: If warmer than 74°F (23°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 68°F (20°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 help it soften and warm. Full troubleshooting guide and video here.
Though technically optional, using quick-toasted sugar will dramatically tame the sweetness of this buttercream, while also adding subtle depth of flavor. It's a make-or-break detail for simple vanilla buttercream, but not nearly so vital when intense flavorings, like melted chocolate or peppermint extract, come into play.
|Nutrition Facts (per serving)|
|Servings: 48 to 50|
|Amount per serving|
|% Daily Value*|
|Total Fat 9g||12%|
|Saturated Fat 6g||29%|
|Total Carbohydrate 6g||2%|
|Dietary Fiber 0g||0%|
|Total Sugars 6g|
|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.|