Mousseline Buttercream

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This buttercream is very light, smooth and incredibly easy to work with. It is soft enough for beautiful shell borders yet strong enough to pipe roses. Liqueur gently perfumes the buttercream, and if it is tinted it also enhances the color. Mandarine Napoléon, for example, lends the palest aura of apricot.
It is a thrilling buttercream to prepare because it starts out looking thin and lumpy, and, about three-fourths of the way through, starts to emulsify and turn into a luxurious cream.
A word of caution; If the butter is too soft or the room too hot, what could have been a satin-smooth cream breaks down into a grainy, hopeless puddle. Once the buttercream is made, however, it holds up better than any other.
Be sure to try the fruit variations. They are all superb. It is excellent with both chocolate and non-chocolate butter cakes and génoise.

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  • 5

Ingredients

  • 2 cups unsalted butter, softened but cool
  • 1 cup sugar
  • 1/4 cup water
  • 5 large egg whites
  • 1/2 + 1/8 teaspoon cream of tartar
  • 3 ounces liqueur, such as Mandarine Napoléon, Grand Marnier, etc.

Preparation

Step 1

In a mixing bowl, beat the butter until smooth and creamy and set aside in a cool place.

Have ready a heatproof glass measuring cup near the range.

In a small heavy saucepan (preferably with a nonstick lining) heat 3/4 cup sugar and the 1/4 cup water, stirring constantly, until the sugar dissolves and the mixture is bubbling. Stop stirring and reduce the heat to low

In another mixing bowl, beat the egg whites until foamy, add the cream of tartar and beat until soft peaks form when the beater is raised. Gradually beat in the remaining 1/4 cup of sugar until stiff peaks form when the beater is raised slowly. Increase the heat and boil the syrup until a thermometer registers 248° to 250°F (the firm ball stage). Immediately transfer the syrup to the glass measuring cup to stop the cooking.

Pour a small amount of the syrup over the whites with the mixer off. Immediately beat at high speed for 5 seconds. Stop the mixer and add a larger amount of syrup. Beat at high speed for 5 seconds. Continue with the remaining syrup. For the last addition, use a rubber spatula to remove the syrup clinging to the glass measuring cup. Lower the speed to medium and continue to beating up to 2 minutes or until cool. If not completely cool, continue beating on the lowest speed.

Beat in the butter at medium speed 1 tablespoon at a time. At first the mixture will seem thinner, but will thicken beautifully by the time all the butter is added. If at any time the mixture looks slightly curdled, increase the speed slightly and beat until smooth before continuing to add more butter.

Lower the speed slightly and drizzle in the liqueur. Place in an airtight container. Rebeat lightly from time to time to maintain a silky texture. Buttercream becomes spongy on standing.

CHOCOLATE MOUSSELINE
BEat in 5 ounces of melted and cooled extra bittersweet or bittersweet chocolate.

WHITE CHOCOLATE MOUSSELINE
Beat in 6 ounces melted and cooled white chocolate, preferably Tobler Narcisse.

FRUIT MOUSSELINE
Add up to 3/4 cup lightly sweetened strawberry or raspberry puree or orange, lemon, passion or lime curd.

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