Neoclassic Mousseline Buttercream Has Arrived

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Our queen of buttercreams has a new version. A couple of days ago, Jean asked on our Ask a Question page if the neoclassic method used for the neoclassic buttercream could also be implemented for the mousseline buttercream. This method eliminated the need for a temperature reading by replacing the sugar and water mixture with a sugar and corn syrup mixture. When the mixture reaches a full boil it automatically is the perfect temperature for heating the egg yolks.


I first offered neoclassic buttercream in The Cake Bible 30 years ago and in the years following, I had not found a favorable result using the same method for Italian meringue. But when testing recipes for Rose’s Baking Basics I was inspired to revisit the technique, altering the ratio of sugar to corn syrup and it worked.
Thanks to Jean’s request we decided to give the new neoclassic Italian meringue a try for the mousseline and after two tests: Eureka!
To prevent the mousseline from becoming curdled, the temperature range for combining the butter and egg white meringue is a couple of degrees higher than for my classic mousseline. This is because it uses less egg white for more strength, and also, while the temperate of the syrup is close to that of the classic one, it is a little lower and therefore a little less stable. Also, we found it beneficial to increase the amount of sugar and corn syrup slightly, compared to the new neoclassic Italian meringue because this also increases stability needed for incorporating butter into it.


Makes: 450 grams/2-1/4 cups (Double the recipe for two 9 inch layer cakes or one 9 by 13 inch sheet cake.)

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Mise en Place

* 30 minutes to 1 hour ahead, set the butter on the counter at cool room temperature. The butter needs to be 65˚ to 68˚F/19˚ to 20˚C.

* 30 minutes to 1 hour ahead, in a small bowl, weigh or measure the egg whites, and add the cream of tartar. Cover with plastic wrap.

* Have ready a 1 cup/237 ml glass measure with a spout by the cooktop.

Make the Mousseline

1) In the bowl of a stand mixer fitted with the flat beater, beat the butter on medium-high speed until creamy, about 1 minute. Set it aside in a cool place (no higher than 70˚F/21˚C).

2) In a small heavy saucepan, preferably with a nonstick lining, with a spout, stir together the sugar and corn syrup until all of the sugar is moistened. Heat on medium, stirring constantly, until the sugar dissolves and the mixture begins to simmer. Stop stirring and reduce the heat to low. (On an electric range remove the pan from the heat.)

3) With a handheld mixer, beat the egg whites and cream of tartar on medium-low speed until foamy. Raise the speed to high and beat until stiff peaks form when the beater is raised slowly.

4) Increase the heat until the sugar and corn syrup has reached a rolling boil with the surface covered with large bubbles. Immediately pour the syrup into the glass measure to stop the cooking.

5) Beat the syrup into the egg whites in a steady stream. Don't allow the syrup to fall on the beaters or they will spin it onto the sides of the bowl. Use a silicone scraper to remove the syrup clinging to the measure and scrape it onto the bottoms of the beaters. 

6) Lower the speed to medium and continue beating for up to two minutes. Refrigerate the meringue for 5 to 10 minutes, until 72˚F/23˚C. Whisk it after the first 5 minutes to test and equalize the temperature.

7) Set the mixer bowl containing the butter in the stand and attach the whisk beater. Beat the butter on medium-high speed for about 3 minutes, or until it lightens in color and is between 70˚F/21˚C and 72˚F/23˚C.

8) Confirm that both the creamed butter and the meringue are both within 2 degrees of each other.

Scrape the meringue into the butter and beat on medium speed until smooth and creamy. Beat for about 2 minutes, scraping down the sides of the bowl as necessary. At first the mixture will look slightly curdled. Continue beating until it becomes a uniform, creamy texture.

If it starts watering out or continues to be curdled, check the temperature.

It should feel cool and be no lower than 70˚F/21˚C, no higher than 73˚F/23˚C. If too warm, set it in a bowl of ice water, stirring gently to chill it down before continuing to beat the buttercream by hand until smooth. If in doubt, it is best to remove a small amount and try beating it either chilling or heating it slightly.

If too cool, suspend the bowl over a pan of very hot water (do not let the bottom of the bowl touch the water) and heat for just a few seconds, stirring vigorously when the mixture just starts to melt slightly at the edges. Dip the bottom of the bowl in a larger bowl of ice water for a few seconds to cool it. Remove the bowl from the ice water and beat the buttercream by hand until smooth.

If the mixture breaks down and will not come together, it can still be rescued. See our posting: When Tragedy Strikes Your Mousseline Buttercream.

9) Gradually beat in the vanilla and optional liqueur.

Store Airtight: room temperature, 1 day; refrigerated, 3 days; frozen, 2 months.


* High fat butter is a great help for decreasing any initial curdling of the mousseline.
* It is best to avoid making meringue on humid days.
* The mixer bowl and beater must be entirely free of any fat, which includes oil or egg yolk.
* If doubling the recipe it’s fine to use a stand mixer for the egg whites if you have a second bowl. Add the heated sugar and corn syrup mixture in 3 parts with the mixer off. Then beat each part for several seconds and scrape the sides of the bowl between each addition. Use a silicone spatula to remove the syrup clinging to the measure and scrape it onto the bottoms of the beater.  When pouring, be sure to avoid letting the syrup hit the beaters so that it doesn’t spin it onto the sides of the bowl.
* The mousseline becomes spongy and fluffy on standing which is lovely once on the cake. If you don’t use it right away, whisk it lightly by hand to maintain a silky texture before apply it to the cake. Do not, however, rebeat chilled mousseline until it has reached 72˚ to 74˚F/23˚C to prevent it from breaking down.

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