Swiss Meringue Buttercream

Swiss meringue buttercream is the frosting I reach for when I want something that tastes elegant rather than just sweet, with a silky, cloud-like texture that is unlike anything you can buy at the store. It is less sweet than American buttercream, more stable than whipped cream, and has a smooth, melt-in-your-mouth quality that makes every cake taste more professional. It pairs beautifully with my vanilla cake or vanilla cupcakes for a combination that never fails.

Why This Recipe Works

Swiss meringue buttercream gets its silky texture from a process called the Swiss method, which involves cooking egg whites and sugar together over a double boiler before whipping them into a meringue. This is different from Italian meringue buttercream, which uses a hot sugar syrup poured into already-whipping egg whites, and from easy buttercream, which skips the cooking entirely.

Cooking the egg whites with the sugar serves two purposes. First, it dissolves the sugar completely, which is what gives SMBC its smooth, non-gritty texture. American buttercream made with powdered sugar always has a slightly grainy finish by comparison. Second, it gently pasteurizes the egg whites so they are safe to eat in their uncooked meringue form.

The meringue needs to cool to room temperature before the butter goes in because fat and heat do not mix well. Butter that is too warm will melt into the meringue instead of emulsifying with it, which is why chilling the meringue for 10 minutes is a non-negotiable step. When the butter is added correctly at the right temperature, the proteins in the meringue trap tiny air bubbles throughout the fat, creating that signature light, whipped texture.

The final step of switching to the paddle attachment and mixing on low for 15 to 20 minutes is what separates a good SMBC from a great one. The paddle pushes out air bubbles and gives the buttercream an ultra-smooth, almost satin-like finish that is perfect for sharp edges and detailed piping.

Swiss Meringue Buttercream Ingredients

Here is everything you need to make Swiss meringue buttercream. Five ingredients, and each one plays a specific role.

Fresh egg whites create a more stable meringue than carton egg whites. Separating eggs yourself gives you the best results. The leftover egg yolks can be used for Boston cream pie or creme brulee so nothing goes to waste.

Granulated sugar dissolves into the egg whites over the double boiler and is what gives SMBC its smooth, non-gritty texture. Do not substitute powdered sugar here.

Unsalted butter must be at room temperature, soft enough to dent easily with your finger but not greasy or melting. This is the most important ingredient to get right. Cold butter will not emulsify into the meringue and warm butter will melt it. Salted butter can be used but will affect the flavor and you should omit the added salt.

Vanilla extract is the primary flavor of Swiss meringue buttercream, so quality matters. A good vanilla bean paste or pure vanilla extract makes a noticeable difference. Nielsen Massey is a great brand that uses sustainable practices.

Salt balances the sweetness and enhances the butter flavor. Do not skip it.

Swiss Meringue Buttercream Step-By-Step

PRO TIP: Wipe your bowl out with white vinegar first. A very clean metal bowl works best because meringue whips up more easily in metal than plastic.

1. Set up your double boiler. Fill a large pot with about 2 inches of water and bring it to a simmer. Place the metal bowl of your stand mixer on top of the pot. The water should not touch the bottom of the bowl.

2. Combine and cook. Whisk together the egg whites, sugar, and salt in the mixing bowl.
   
   Cook the egg white mixture until it reaches 110 degrees, whisking constantly along the sides of the bowl to distribute the heat evenly. If you do not have a thermometer, rub a bit of the mixture between your fingers. When you can no longer feel any sugar granules, it is done.

3. Whip the meringue. Remove the bowl from the heat and transfer it to your stand mixer with the whisk attachment. You can use a hand mixer and a large bowl if needed, but it will take considerably longer. Whip on medium-high speed for 10 to 15 minutes until you reach glossy, stiff peaks. The meringue should be bright white and hold a firm shape.

4. Cool the meringue. Pour the meringue into a shallow dish and refrigerate for about 10 minutes to cool it to room temperature. You can also leave it in the bowl and refrigerate, but it will take longer to cool. Do not skip this step. Warm meringue will melt your butter and turn your buttercream into soup.
   

5. Add the butter. Once the meringue is cooled, return it to your stand mixer with the whisk attachment. Add the room-temperature butter and vanilla and mix until fully combined.
   

6. Whip until fluffy. Whip the buttercream on medium-high speed until it is white, fluffy, and no longer tastes buttery. This takes 8 to 10 minutes. Pro tip: add a drop or two of violet gel food coloring to counteract the yellow from the butter and make your buttercream brighter white.
   

7. Finish with the paddle. Switch to the paddle attachment and mix on low speed for 15 to 20 minutes. This removes air bubbles and creates an ultra-smooth, silky texture. This step is optional but if you want that perfectly creamy, professional finish, do not skip it.
   

Batter & Frosting Calculator

This recipe makes enough to frost and fill a two-layer 8-inch cake or frost about 24 cupcakes. Store leftovers in an airtight container in the fridge for 1 week or freeze for up to 6 months.

Common Mistakes To Avoid

Using carton egg whites. Carton egg whites are pasteurized at high heat which denatures some of the proteins and makes them harder to whip into a strong, stable meringue. Fresh egg whites from whole eggs give you a much more reliable result.

Any fat in the bowl. Even a trace of fat from egg yolk or residue will prevent your egg whites from whipping properly. Wipe your bowl and whisk with white vinegar before starting to remove any grease.

Not cooking to the right temperature. The egg white and sugar mixture needs to reach 110 degrees, and all sugar granules need to be fully dissolved. Under-cooking leaves a gritty texture in the finished buttercream.

Adding butter to warm meringue. This is the most common failure point. If the meringue is still warm when the butter goes in, the butter melts and the buttercream looks like soup. Cool the meringue to room temperature before adding any butter, no exceptions.

Butter that is too cold. Cold butter will not emulsify smoothly into the meringue and will leave lumps. Your butter should be soft enough to press your finger into easily but still holding its shape.

Stopping too soon. SMBC goes through a curdled, broken-looking stage before it comes together. Many people panic and stop at this point thinking it has failed. Keep mixing. It will come together into a smooth, fluffy buttercream within a few minutes.

Skipping the paddle step. The whisk incorporates air, which gives you volume. The paddle removes excess air, which gives you smoothness. If you want a truly silky finish for sharp-edged cakes, the 15 to 20 minutes on the paddle makes all the difference.

Swiss Meringue Buttercream FAQs

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