Swiss Meringue Buttercream

Swiss Meringue Buttercream is easy to make, perfectly sweetened, and has a light, silky texture. It is the perfect topping for cakes or cupcakes! Its silky texture makes it the best frosting to achieve that perfectly smooth coating on a layer cake.

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Swiss meringue buttercream (SMB) is delicious and stable: the buttercream version of the best friend who always has your back and will pick up your call no matter the time! This SMB is delicately sweetened, light and silky. It almost melts in your mouth!

This buttercream is perfect to use on these vanilla cupcakes or to frost this yellow cake. It is versatile to fit your flavor and sweetness. Looking for an even more stable buttercream be sure to check out this [Italian meringue buttercream].

Ingredients & Substitutions

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• Egg Whites: These form the structural base of the buttercream. Separate your eggs cold, then let the whites come to room temperature before you start — room temperature whites whip faster and to greater volume than cold ones just like when making this [white cake recipe].
• Granulated Sugar: Dissolves into the whites over heat, creating the syrup that becomes your meringue. Do not substitute powdered sugar here; the cornstarch it contains will make the final buttercream gummy.
• Unsalted Butter: This is the most critical ingredient, and the temperature matters more than almost anything else in this recipe. Butter that is too warm will make the emulsion soupy; butter straight from the refrigerator will make it dense and lumpy. You want it cool but still pliable, meaning it bends without cracking and leaves an indent when pressed, but does not feel greasy or soft at the edges.
• Vanilla Extract: Adds warmth and rounds out the flavor. Pure vanilla extract is my preference here; imitation vanilla will work, but it tends to read slightly artificial in an uncooked frosting where the flavor has nowhere to hide.

See the recipe card for full information on ingredients and quantities.

Variations on This Swiss Meringue Buttercream

• Jam or Jelly. Fold in up to ¾ cup of jam or jelly after the buttercream comes together, adding it a spoonful at a time so it incorporates without breaking the emulsion. My Mixed Berry Jam works beautifully here.
• Caramel. Swap up to ¾ cup caramel sauce for a rich, buttery variation, which is what I do for my Caramel Swiss Meringue Buttercream. Make sure the caramel is fully cooled before adding it, or it will melt the butter.
• Lemon Curd. Add up to ¾ cup lemon curd for a bright, tart frosting that cuts through rich cakes beautifully. My Lemon Swiss Meringue Buttercream gives you the full method with ratios dialed in.
• Chocolate. Fold in up to 7 oz of melted chocolate, making sure it has cooled to room temperature before adding so it does not seize or melt the butter. For the complete version, see my Chocolate Swiss Meringue Buttercream.

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Professional Tips

• Adding the salt to meringue adds stability. Most recipes call for the salt to be added in at the end, but I like to make my ingredients work for me. Adding the salt to the meringue before cooking will stabilize the meringue and add flavor. And now you are baking like a professional chef too.
• Know its limits. It is the most stable when refrigerated but tastes the best at room temperature. If possible, I allow the whole cake to sit at room temperature for at least 2 hours prior to serving. You can also slice it cold then allow it to sit to ensure perfect slices.
• Weigh ingredients for the best results. There can be a 30% difference in the weight of one egg white depending on the size of the egg yolk. This means that the resulting meringue will be more or less stable depending on the ratio of egg white to sugar. For the average baker this does not matter, but if you are going to entrust a wedding cake to this buttercream, weigh your ingredients.
• People stress too much about fat in meringues. Here is the real talk: as long as there are no visible yolks in the whites and your bowl feels clean, then you are fine. Wiping out your bowl with vinegar is unnecessary and will impact the flavor. If your meringue is not whipping up, add cream of tartar by the teaspoon until it does. If you can taste it in the final meringue, then start again, but you probably won’t have to. Life is too short to stress about meringue.
• If it looks broken, keep mixing. A curdled or soupy buttercream is not ruined. If it is soupy, refrigerate the bowl for 20 to 30 minutes and continue mixing. If it looks curdled, keep the mixer running: the friction and emulsification will bring it back together.
• A kitchen torch can rescue stubborn butter chunks. If a few pieces of butter refuse to incorporate, run a kitchen torch briefly around the outside of the bowl to soften them. Work quickly and keep the torch moving so you do not melt the surrounding butter beyond recovery.

How to Make Swiss Meringue Buttercream

Use these instructions to make the perfect Swiss Meringue Buttercream.

This is the setup that makes the gentle, even heat possible, so take a moment to check the fit before you add anything to the bowl.

Step 1: Set up your double boiler. Fill a medium saucepan with about an inch of water and bring it to a simmer over medium heat. Nest your stand mixer bowl inside — you want it to sit above the water without touching it.

Step 2: Whisk together the egg whites, sugar, and salt over the double boiler. Combine everything in the mixer bowl and set it over the simmering water. Whisk constantly as it heats: the mixture will start thin and granular, then gradually turn warmer and smoother as the sugar dissolves. You are looking for 130°F on an instant-read thermometer, or until you can rub a bit between your fingers and feel no graininess at all. The mixture will have gained a little volume and feel noticeably lighter by the time it is ready.

Step 3: Whip the meringue to stiff peaks. Transfer the bowl to your stand mixer fitted with the whisk attachment. If you have a gas burner, the bowl will be genuinely hot, so use a towel to handle it. Beat on high speed until the meringue reaches stiff, glossy peaks and the outside of the bowl feels only slightly warm to the touch, which is completely normal and exactly what you want before adding the butter. Rushing this step is the most common reason buttercream breaks.

Step 4: Add the butter and beat until silky. Switch to the paddle attachment and add all the butter at once. Beat on medium speed and give it time. The mixture will look curdled and broken for several minutes, which is completely normal — keep going. Eventually it will suddenly pull together into a smooth, silky buttercream that looks almost too good. That transformation is my favorite part of this whole process.

If your buttercream looks like soup rather than curdled, the meringue was likely still too warm when you added the butter. Let the butter work in completely anyway, then place the entire bowl and paddle attachment in the refrigerator for 20 to 30 minutes and continue mixing. The number one rule here is patience.

Step 5: Troubleshoot any stubborn butter bits. If there are a few small chunks that refuse to incorporate, run a kitchen torch briefly around the outside of the bowl to gently warm those spots. Keep the torch moving and do not linger in any one place, or you risk melting the surrounding butter — and at that point there is no recovering the batch.

Step 6: Add vanilla and whip to finish. Switch back to the whisk attachment, add the vanilla extract, and beat until the buttercream is light, fluffy, and fully aerated. This is what I always do last: the whisk gives it that final lift that makes it spreadable and smooth right out of the bowl.

Recipe FAQs

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Before You Go

If this silky, cloud-like buttercream has you thinking about what else you could frost, pipe, or fill, browse my Buttercream and Frosting Recipes or make this [ermine frosting] next!