Italian meringue buttercream is the lighter, fluffier, more stable cousin to the ever popular Swiss meringue buttercream. Both Italian and Swiss buttercreams are similar as they are light, silky smooth, and melt in your mouth. They both create a smooth cake surface and chill firmly for sturdy stacking and transportation. The main difference between Swiss and Italian is in the preparation of the meringue.
The Italian method of boiling sugar and water to a high temperature to create a sugar syrup and then adding it to soft peak egg whites, allows for a more stable meringue, or a meringue that will not deflate or breakdown easily over time. This is especially beneficial when using this buttercream for a cake for an outdoor event or on a warm day. With caution of course. If you frost a cake with any butter based buttercream and leave it outside in the sun in mid-July in the Midwest, it's destined to be a buttery messy puddle quickly. But, for moderately warmer temps, it is the best butter based buttercream to use.
Both Swiss and Italian meringue buttercream contain mostly the same ingredients - egg whites, sugar, butter, salt and flavoring. The exception is that Italian meringue buttercream usually uses some sort of stabilizer (cream of tartar, salt) which stabilizes the egg whites during beating, before the sugar syrup is added.
How to make Italian meringue buttercream
Italian meringue buttercream is made by combining sugar and water into a saucepan and boiling until softball stage, or about 240-245F. As with caramel, mix together the sugar and water. Then stop stirring. You don't want to create sugar crystals - which would give you crunchy bits in your otherwise silky smooth buttercream. While the sugar is boiling, whip up the egg whites and cream of tartar in the bowl of a stand mixer with a whisk attachment until soft peaks form. When the sugar mixture reaches temperature, remove from the heat and turn your mixer up to medium-high speed. Drizzle the *very* hot sugar mixture into the bowl, between the side of the bowl and the whisk attachment.
Continue to mix on medium-high until the outside of the bowl is just lukewarm to the touch, or the mixture is at 80F. Really though, don't stress about having exactly 80F meringue here -I'm really just giving you a temperature as a guide. Just feeling that the bowl is lukewarm means it's ready for the butter. You can wrap the bowl with ice packs or cold towels to help cool the meringue down faster if you wish.
Same as with Swiss buttercream, softened butter is added to the bowl piece by piece until all the butter is added. The buttercream will deflate a bit, and it is quite possible the buttercream will curdle or look thin, like cake batter, but keep going. Oftentimes, meringue buttercreams go through an ugly, sloppy mess before coming together and looking more like buttercream. Once the buttercream has come back together, let it mix on low speed for a while - 5-10 minutes or so, to get rid any air bubbles. Air bubbles in buttercream under a fondant cake can result in blow-outs and bubbling fondant. The end result will be perfectly smooth, beautiful, fluffy, light and silky buttercream.
Troubleshooting Italian meringue buttercream
*The buttercream can be refrigerated and also freezes well. Bring to room temperature before rewhipping, otherwise the buttercream will separate. If this happens, heat the metal mixing bowl with a kitchen torch while continuing to whip. Stop applying heat when the buttercream comes together.
*Color meringue buttercream with gel color, or ideally chocolate colors (which are oil based). Do not use liquid color as it can dilute the buttercream.
*If at the end of mixing, your buttercream is a liquidy, soupy mess, pop in the refrigerator for 15-25 minutes to cool it down. Look for the edges of the buttercream to start to harden, then it should be ready to whip again. Repeat this process again if necessary.
*Keep going! If you have whipped up your egg whites and heated your syrup to the correct temperature, the rest of the process is pretty foolproof. If it is curdled, separated, lumpy, the butter was too cold, etc. Keep mixing. It might take a bit longer but keep mixing and it will come together.
*Italian meringue buttercream can hold quite a bit of flavorings. When adding liquids, such as fruit purees and other liquids, mix in a little at a time. The liquid needs to be able to emulsify into the buttercream. Another reason you want to add a little bit of liquid at a time, is that adding too much liquid can cause the buttercream to become unstable. I recommend reducing your fruit purees into concentrates before adding to the buttercream. You can also use pulverized freeze dried berries for fruity variations as well.
The recipe below is for vanilla bean Italian meringue buttercream. But the flavor options are endless. Here are a few popular flavors to experiment with. Adjust the quantities to suit your taste. I like my buttercream flavors as concentrated as possible.
*Chocolate – Add 3 cups (600g) bittersweet chocolate, melted and cooled to room temperature, to a batch of buttercream
*Fruit flavors – Add 1 to 1 ½ cups reduced fruit puree, preserves or curd per batch
*Nut Butters, Cookie Butters, Caramel- Add 1 to 1 ½ cups per batch
*Boozy – Add ¼ – ⅓ cup flavored liqueur such as Bailey’s, Champagne, Amaretto, etc. per batch
For more information on meringue based buttercream, check out my post on Swiss meringue buttercream here.
Italian Meringue Buttercream
- 9-10 (300g) large egg whites
- ¼ teaspoon cream of tartar
- 2 ½ cups (500g) granulated sugar
- ½ cup (120g) water
- 3 ½ cups (793g) unsalted butter, room temperature, cubed
- ¼ teaspoon fine sea salt
- 1 tablespoon vanilla bean paste
- Place the egg whites into the bowl of a stand mixer fitted with the whisk attachment.
- In a heavy bottomed saucepan, combine the sugar and the water over medium-high heat. Stir to moisten the sugar.
- Clip a candy thermometer to the side of the saucepan. Boil the sugar and water mixture. Do not stir.
- Meanwhile, whisk the egg whites on medium speed until foamy, about 1 minute. Add the cream of tartar.
- On medium speed, whisk the egg whites to soft peaks, about 1-2 minutes.
- When the sugar syrup reaches 240F, remove the saucepan from the heat. Turn the speed of the mixer to high, and very carefully and slowly pour the hot syrup in a thin and steady stream into the bowl, pouring between the bowl and the whisk attachment so that the sugar syrup doesn't splatter. Don't rush.
- Once the sugar syrup is added, continue to whip until stiff peaks form and the bowl is lukewarm to the touch, about 10-15 minutes. You can wrap the bowl with ice packs to speed up this process, if you wish.
- Switch to the paddle attachment. With the mixer on low speed, add the softened butter, a few pieces at a time, mixing until the butter disappears into the meringue.
- After all the butter has been added, increase the speed to medium and whip until thick, and fluffy.
- Reduce the speed to low. Add the vanilla and salt, and beat for an additional 5-10 minutes to minimize the air bubbles.