While I frost most of my cakes with American buttercream, sometimes I like to mix things up! One of my resolutions this year was to be more open to different types of frosting, and I’ve stuck to it! After a bit of trial and error, I feel like I have finally mastered Swiss meringue buttercream frosting (SMBC).
This type of frosting definitely takes a bit more effort and time than my American buttercream, but it isn’t as difficult to make as you might think.
It also is a bit more stable, and less finicky once it’s made! My favorite thing about swiss meringue is that it doesn’t crust. You don’t have to cover it with plastic wrap, or worry about your frosting crusting on your cake if you make it in advance.
After what feels like a zillion batches, I found that I prefer mine with a bit more salt and slightly less butter than most SMBC recipes call for.
While half the battle of SMBC is having a good recipe, the other half is how you make it! That’s why I’m also walking through everything you need to know to make the smoothest, fluffiest swiss meringue buttercream frosting in this post.
Step #1: Room Temp Egg Whites
What gives this frosting its incredible texture is the meringue that it’s made with. That’s why the eggs in this recipe are so important. Or more specifically the egg whites!
If you’re not quite sure what to do with the 7 egg yolks you’ll be left with after making this frosting, here’s a great post with loads of ideas for using up leftover egg yolks.
You want to make sure your egg whites are at room temperature when you make this frosting. Room temperature egg whites whip up better and faster than egg whites that are cold.
I suggest separating your eggs about an hour before you plan to make your frosting. Be careful as you do this, because they won’t whip up properly if any yolk gets into the mixture!
If you forget to take your eggs out of the fridge, you can always pop them into a bowl of warm water for 5 minutes to quickly bring them to room temperature.
Normally I’m a huge fan of using egg whites out of a carton, but that’s when I’m adding them into a batter. When it comes to making meringue, I find that carton egg whites simply don’t whip up as well.
I really struggle getting stiff peaks with them. I’m not sure if the pasteurization process does something to the protein in the egg or what, but I don’t recommend using egg whites from a carton to make swiss meringue frosting.
Step #2: Making The Egg Whites Safe to Eat & Knowing When The Mixture is Hot Enough
There’s something about the idea of adding raw eggs into frosting that seems a bit creepy. A lot of people worry it isn’t safe to eat, but we take an important step to ensure it is!
By heating up our egg whites and granulated sugar with a double boiler to 160 degree Fahrenheit, we accomplish two things at once.
The first is that we kill any potentially harmful bacteria. Salmonella is instantly killed at temperatures above 160 degrees F.
The easiest way to ensure your mixture gets hot enough is to use a digital thermometer. This helps you know exactly when your egg whites are warm enough, and prevents you from overheating them.
If you don’t have a digital thermometer on hand, you can test with your finger. The mixture should be quite warm to the touch, but not hot enough to hurt or burn your finger.
The second thing we accomplish is dissolving the granulated sugar, which gives the frosting a silky smooth texture.
It’s very important that the sugar is fully dissolved before you make your meringue, or else your frosting can end up with a grainy texture.
A great way to know your mixture it ready if you don’t have a thermometer is the finger test! Take a tiny bit of the warm liquid between your forefinger and thumb, and rub them together.
The mixture should be smooth, and you shouldn’t be able to feel any sugar granules. If you do, I suggest heating your egg white/sugar mixture a bit longer then testing again to make sure it’s smooth.
Step #3: Making Stiff Peaks
Once your sugar is fully dissolved and your mixture is smooth, it’s time to whip it into a meringue with stiff peaks. This takes quite a bit of time!
I find it takes me about 10 minutes of mixing with a whisk attachment on a medium high speed.
You could in theory make this swiss meringue frosting with a hand mixer, but it would take forever!! Making it with a stand mixer is much easier and quicker.
Stiff peaks should look like my whisk below, where the meringue can stand up on its own when flipped upside down.
It can be hard to tell when the meringue reaches this stage just by looking at your mixing bowl, so feel free to take breaks and test it by removing your whisk attachment.
Doing so won’t have a negative impact on your meringue. It just helps make sure you get the consistency just right without over mixing your meringue.
Step #4: When and How to Add in Your Butter
Once your meringue has stiff peaks, it’s time to mix in the unsalted butter.
After all that mixing you’d think your bowl would have fully cooled off, right? But you might be wrong! At this point in time I like to feel that bottom of my bowl with my hand.
If it feels pretty much room temperature, I add in my butter. If it still feels warm, I’ll either wait another 15 minutes to add the butter or pop my bowl into my fridge for 5 minutes to help it cool down.
Usually by making sure your meringue and bowl have cooled to room temperature, you can prevent your swiss meringue buttercream frosting from becoming too thin or soupy.
When I do start to add in my unsalted butter, I do it in small chunks (about 1 Tbsp at a time). This gives your meringue time to incorporate the butter, and helps it mix together more easily.
As you add your butter, it’s super important that your butter is room temperature. This does NOT mean soft to the touch, or greasy.
Most sticks of butter come to room temp in about an hour, so be sure your butter doesn’t sit out much longer than that or it may become too soft.
It should be soft enough for you to be able to press your finger into, but firm enough that you have to apply a bit of pressure to do so.
Step #5: The Attachment Switcheroo
When all your butter is mixed in and you’ve added in your salt and vanilla, it’s time to swap out your whisk attachment!!
While we want our buttercream to be fluffy and light in texture, we also want it to be smooth.
Whether you plan to spread your frosting onto a cake or pipe with it, your frosting needs to be smooth and air bubble free.
I find that mixing your finished frosting on a low speed with a paddle attachment for a few minutes makes a world of a difference.
This makes it way easier to smooth onto cakes!!
Two of the most common issues people run into when this type of frosting are curdled or soupy frosting.
While it might seem terrifying to watch your frosting seem to fall apart, fear not. Both problems are actually pretty easy to fix!!
How to Fix Curdled / Broken Swiss Meringue Buttercream
A lot of different things can cause your SMBC to break or curdle.
Maybe your butter was too cold, or your kitchen was too chilly. Maybe you were thawing a batch of buttercream made in advance, and it hadn’t fully come to room temperature before you started mixing it.
Whatever the reason, your frosting looks chunky, dense, and greasy.
But don’t worry, your frosting isn’t ruined! There’s an easy work around that will bring your frosting back together.
Simply place your bowl over a hot water bath / double boiler until the frosting around the edge of the bowl has melted. Then give it a good mix for several minutes.
The melted, warm frosting around the edge of the bowl will mix with the frosting that’s too cold. This will bring the overall temperature of your frosting up to the right temperature and allow it to become smooth again.
How to Fix Soupy Swiss Meringue Buttercream
On the other hand, if your frosting is too warm it might become a soupy, runny mess. This can happen if your meringue is too warm when you add your butter, if your butter is too warm, or if your kitchen is too toasty!!
If your frosting isn’t sturdy enough to keep its shape, you need to cool it down. To do this, just pop your mixing bowl and whisk right into the fridge.
I like to chill my bowl for about 20 minutes. At this point the center might still be a bit soupy, but the frosting along the sides of the bowl should be firmer. I mix it for a few minutes to see if it comes together.
If after 3-4 minutes of mixing it still looks too soft, I chill the bowl for another 10 minutes before mixing it again. That usually does the trick!
Coloring Your Swiss Meringue Buttercream Frosting
The last thing I want to touch on is coloring swiss meringue buttercream frosting.
This type of frosting is a bit more difficult to color than American buttercream. To make it bright and colorful, gel food coloring is a must.
My favorite gel food coloring is Americolor, and it’s the only food coloring I use.
Even with gel food coloring, I find I have to use quite a bit to get my colors really vibrant.
If you want make deep or really intense colors, I highly recommend making your frosting in advance. The color of the frosting will deepen overtime!
Tips For Making Best Swiss Meringue Buttercream Frosting:
- Traces of grease in your mixing bowl can prevent your meringue from forming stiff peaks. You can wipe down your tools with lemon juice or vinegar to make sure they’re grease-free.
- Use room temperature egg whites; they whip up more quickly and easily than cold egg whites
- Heat your egg white / sugar mixture to 160 degrees F and check to make sure all the sugar is dissolved
- Whip your meringue until your peaks are stiff enough to defy gravity
- Make sure your butter is actually at room temp, and add it in slowly (1 Tbsp at a time)
- When in doubt (if your frosting breaks / curdles), just keep mixing!! It should come back together with the help of your stand mixer
- Mix your finished buttercream on the lowest speed with a paddle attachment for a few minutes to make it smooth
- 1 batch of frosting is enough to fill and frost a seven or eight inch layer cake.
Making This Swiss Meringue Frosting in Advance and Storage Tips:
- Make your frosting ahead of time or save any leftover frosting! It can be stored in an airtight container at room temperature for 1-2 days, in the fridge for up to a week, or in the freezer for up to 3 months.
- Be sure to give it a good stir once it thaws to room temp to get the consistency nice and smooth again.
- A frosted cake can last in the fridge for up to a week, or in the freezer for up to a month. The buttercream locks in all the moisture, keeping the cake fresh and delicious!
- If you cut into the cake and have leftovers, use any remaining frosting to cover the cut section to keep it moist and store in the fridge for up to a week.
Let Me Know What You Think of This Swiss Meringue Buttercream Frosting!
If you try this recipe for swiss meringue buttercream frosting, I’d love to hear what think of it! Please leave a rating, and let me know your thoughts by sharing a comment 🙂
Also please tag me @chelsweets, and use the #chelsweets so that I can see your amazing creations on social media!
- 7 large egg whites (235 grams)
- 2 cups granulated sugar (400 grams)
- 2 cups unsalted butter, room temperature (454 grams)
- 1/4 tsp salt (1 gram)
- 2 tsp vanilla extract (8 grams)
- gel food coloring (if desired)
- In a medium sized pot, add about 1 inch of water bring to a simmer.
- Before making the frosting, be sure to thorough clean your mixing bowl; if there’s any grease it can make it difficult to make the meringue.
- Add the egg whites and granulated sugar into your clean mixing bowl.
- Place the bowl on top of the pot filled with simmering water, being sure the water isn’t actually touching the bottom of your bowl. The bowl should create a seal over the pot.
- Whisk the mixture constantly for about 3 minutes, until it reaches 160 degrees F. You can test the mixture to see if it’s ready by rubbing a tiny bit between your fingertips. The sugar should be fully dissolved, and it should feel super smooth and hot to the touch.
- Lift your bowl away from the pot, and dry the bottom with a towel.
- Lock the bowl into place on your stand mixer, and beat on medium high using a whisk attachment. Mix for about 10 minutes, until you have stiff and glossy peaks.
- At this point in time, the bowl should be back to room temperature and no longer warm to the touch. If it’s warm, it will melt your butter!!
- Once bowl is at room temp, swap out your whisk attachment for your paddle attachment.
- Mix on a medium speed and add in the unsalted butter, 1 Tbsp at a time.
- Add in the salt, vanilla extract and purple gel food coloring (if desired) and mix on a low speed until fully incorporated.
- When all butter is mixed in, scrape the sides and bottom of the bowl with a rubber spatula and continue mixing for about 3 minutes.
- The frosting should have a thick whipped consistency at this point. If it looks lumpy or broken, keep mixing until it looks smooth and thick.
One batch is enough to fill and frost a 7 or 8" layer cake, or enough to frost three dozen cupcakes.
Make your frosting ahead of time or save any leftover frosting! It can be left out at room temperature for 1-2 days, stored in an airtight container in the fridge for up to a week, or in the freezer for up to 3 months. Be sure to give it a good stir once it thaws to get the consistency nice and smooth again.
A frosted cake can last in the fridge for up to a week, or in the freezer for up to a month. The buttercream locks in all the moisture, keeping the cake fresh and delicious!
If you cut into the cake and have leftovers, use any remaining frosting to cover the cut section to keep it moist and store in the fridge for up to a week.
Amount Per Serving Calories 825Total Fat 61gSaturated Fat 38gTrans Fat 0gUnsaturated Fat 20gCholesterol 163mgSodium 170mgCarbohydrates 67gFiber 0gSugar 67gProtein 5g