Swiss meringue buttercream is a smooth, lightly sweet frosting made by warming egg whites and sugar, whipping them into a meringue, then beating in butter. It spreads cleanly, holds piped details, and gives a wedding cake a polished finish; this batch is sized for filling and frosting a three-layer, 8-inch cake.
Ingredients
- 8 large egg whites, about 1 cup (240 g), at room temperature
- 2½ cups (500 g) granulated sugar
- 4 cups (907 g) unsalted butter, softened but still cool, cut into tablespoon-size pieces
- 2 teaspoons (10 ml) pure vanilla extract
- ½ teaspoon (3 g) fine salt
Instructions
- Prepare the equipment. Make sure the mixing bowl and whisk are clean and free of grease; even a little fat can keep egg whites from whipping well. Set a heatproof bowl over a saucepan containing 1 inch (2.5 cm) of gently simmering water. The bottom of the bowl must not touch the water. Have a candy or instant-read thermometer ready, and bring the butter to a cool, pliable consistency while you work.
- Warm the egg whites and sugar. Put the egg whites and sugar in the heatproof bowl and whisk constantly, scraping around the sides, for about 8–10 minutes. The mixture should feel smooth when rubbed between two fingers, with no sugar grains remaining. Check with a thermometer: egg dishes should reach the USDA FSIS safe minimum of 160°F (71°C). Keep whisking as needed to reach that temperature without scrambling the whites.
- Whip the meringue and let it cool. Transfer the hot mixture to a stand mixer fitted with the whisk attachment. Whip on medium-high for 10–12 minutes, until it is glossy, holds stiff peaks, and the outside of the bowl no longer feels warm. If the bowl is still warm, pause and allow the meringue to cool for up to 20 minutes before adding butter; warm meringue can melt it.
- Beat in the butter. Switch to the paddle attachment, or keep the whisk if needed, and add the butter a few pieces at a time on medium speed. Let each addition begin to blend before adding more. The mixture may look soupy or curdled partway through; keep beating for several minutes rather than adding extra butter or sugar. It should eventually turn silky and hold its shape.
- Season and check the texture. Beat in the vanilla and salt. For a spreadable finish, the buttercream should be smooth and soft enough to move easily with a spatula, but not runny. If it feels greasy or loose, chill the bowl for 10 minutes and beat again. If it is stiff because the butter was too cold, warm the outside of the bowl briefly with a warm towel and continue beating.
- Fill and crumb-coat the cake. Use the frosting on a completely cooled cake. Spread an even layer between three 8-inch (20 cm) cake layers, then apply a thin coat over the top and sides to trap loose crumbs. Refrigerate the crumb-coated cake for 30 minutes, until the surface is firm enough to handle without pulling up crumbs.
- Finish the cake. Spread the remaining buttercream over the chilled cake with an offset spatula or bench scraper. Smooth the sides, create soft swirls, or pipe borders and simple rosettes. Keep the cake chilled if it will not be served soon, and let it soften slightly before slicing.
Tips
- Measure the egg whites by weight when possible. Egg sizes vary, so 240 g is more dependable than counting alone. Fresh shell eggs work well. Carton whites can be less predictable for whipping, so check the package directions before substituting.
- Keep every bowl and tool grease-free. Wash and dry the mixing bowl and whisk thoroughly before starting. Separate eggs one at a time into a small cup so a broken yolk does not contaminate the whole batch.
- Use butter that bends without looking shiny. Very cold butter can leave lumps; melted or greasy butter can make the frosting slack. If the buttercream looks curdled after adding butter, continue beating. Temperature changes, not a failed recipe, are usually the cause.
- Plan around the cake’s temperature. Frost only cake layers that are fully cool. A warm cake softens the buttercream and can make layers slide. A chilled crumb coat makes the final layer neater, especially when the cake has several tiers or a dark filling.
Serving Suggestions
This amount is intended to fill and cover a three-layer 8-inch (20 cm) cake, with enough extra for a modest piped border or a few rosettes. The exact amount used depends on how thickly you fill the layers and whether you prefer a smooth, thin finish or generous swirls. If you are frosting a larger cake, a tall cake, or a design with extensive piping, make an additional half batch rather than stretching the frosting too thin.
For the cleanest slices, use a long knife warmed in hot water and wiped dry between cuts. Swiss meringue buttercream tastes best when it is not refrigerator-cold: bring a chilled cake out about 45–60 minutes before serving, depending on room temperature, while keeping total time at room temperature within two hours. This softens the buttercream and makes the cake easier to cut without making the frosting run.
Pair the frosting with vanilla, almond, chocolate, lemon, or berry cake. Its mild sweetness suits tart fruit fillings particularly well. Keep fillings in a thin, even layer and pipe a buttercream dam around the edge if the filling is soft; this helps prevent it from squeezing out when the cake is stacked.
Variations
Vanilla bean: Replace the vanilla extract with the seeds scraped from 1 vanilla bean (about 5 g of seeds). Add them with the salt after the butter is incorporated. The little flecks look lovely on a pale cake, and the flavor is more rounded than extract alone.
Citrus: Add 1 tablespoon (15 ml) finely grated lemon or orange zest after the buttercream becomes smooth. For a sharper flavor, beat in 1 tablespoon (15 ml) strained lemon juice a little at a time. Too much juice can loosen the texture, so keep the amount modest and chill the frosting briefly if it softens.
Chocolate: Melt 6 ounces (170 g) finely chopped semisweet chocolate and let it cool until fluid but no longer warm. Beat it into the finished buttercream. Warm chocolate can melt the butter, while chocolate that is too cool can set into flecks, so check its temperature before adding.
Almond: Replace the vanilla with 1 teaspoon (5 ml) almond extract, or use ½ teaspoon (2.5 ml) almond extract plus 1 teaspoon (5 ml) vanilla. Almond extract is concentrated; start with the smaller amount if you want a delicate flavor. For a nut-free event, check the extract label and avoid cross-contact with nuts.
Color: Use a small amount of gel food coloring after the frosting is fully mixed. Gel colors add less liquid than many liquid colors, which helps preserve the buttercream’s consistency. Add color gradually, since the shade can deepen while the frosting rests.
Storage and Reheating
Because this buttercream contains butter and egg whites, refrigerate the frosted cake or unused frosting within 2 hours. Store the cake in a covered container in the refrigerator for up to 4 days for best quality. If the cake is tiered, follow the cake’s structural needs when chilling and transport it cold; avoid leaving it in a warm car or direct sun.
Refrigerate leftover buttercream in an airtight container for up to 5 days, or freeze it for up to 2 months. Thaw frozen frosting overnight in the refrigerator. Do not microwave or otherwise reheat it: let it come to cool room temperature, then beat it again until smooth. If it looks separated, continue beating; briefly warming the outside of the bowl can help bring the mixture back together. A chilled frosted cake can be brought toward serving temperature at room temperature, but keep its total unrefrigerated time within 2 hours.
Frequently Asked Questions
Will this frosting hold up on a wedding cake?
It is firm enough for smooth sides, borders, and moderate piping when the cake is kept cool. It is still butter-based, so it softens in warm rooms and is not a good choice for prolonged outdoor display in hot weather. Keep the cake refrigerated until display time and ask the venue to keep it in a cool place.
Can I make the buttercream ahead?
Yes. Make it up to 5 days ahead and refrigerate it in an airtight container, or freeze it for up to 2 months. Bring it back to cool room temperature and beat until smooth before using. If you are preparing the whole cake ahead, store it covered in the refrigerator and allow time for it to lose some of its chill before serving.
Why did my buttercream turn soupy or curdled?
It is usually a temperature issue. If the meringue was warm when the butter went in, the butter may have softened too much; chill the bowl for 10 minutes and beat again. If cold butter made the mixture look curdled, keep mixing until it warms slightly and becomes cohesive. Avoid correcting either problem with extra sugar, which changes the sweetness and texture.
Can I use salted butter?
Unsalted butter gives you better control over the final flavor. If salted butter is all you have, use it and leave out the ½ teaspoon (3 g) of salt in the recipe. Salt levels differ by brand, so taste the finished buttercream before deciding whether it needs a tiny pinch.
Can I make this without a stand mixer?
A sturdy hand mixer can work, but whipping the meringue and incorporating the butter will take longer and require more attention. Use a heatproof bowl that fits the mixer safely, and do not hold the bowl over the steaming saucepan while operating an electric mixer. A stand mixer is more comfortable for this quantity, particularly during the 10–12-minute meringue-whipping stage.
How much frosting should I make for a different cake size?
This batch makes roughly 10 cups of buttercream and is suited to a three-layer 8-inch cake with a moderate coating. A larger diameter, extra-tall layers, thick filling, or extensive piping can require more. For a small two-layer cake, you may have extra; refrigerate or freeze it rather than reducing the recipe unless you can accurately scale the egg whites and sugar.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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