Crème Mousseline Recipe

Make bakery-quality crème mousseline at home with this professional recipe. This rich and silky French buttercream is perfect for filling cakes, tarts, éclairs, and layered desserts. Made from classic pastry cream and whipped butter, it’s a staple in patisserie and holds its shape beautifully for piping and assembling delicate pastries. Ideal for elegant desserts and special occasion bakes.

A silky French buttercream custard that’s perfect for filling cakes, tarts, and pastries.

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Ingredients

For the Pastry Cream (Crème Pâtissière):

• 2 1/2 cups (600g) whole milk
• 5 egg yolks
• 1/2 cup (100g) white sugar, divided
• 3 tablespoons cornstarch
• 1 1/2 tablespoons all-purpose flour
• 1/2 teaspoon salt
• 2 teaspoons vanilla extract

For the Crème Mousseline:

• 4 sticks (450g) unsalted butter, room temperature

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Instructions

Make the Pastry Cream:

1. In a mixing bowl, whisk together the egg yolks, two tablespoons of the sugar, cornstarch, flour, and salt until smooth. Set aside.
2. In a medium saucepan, combine the remaining sugar, milk, and vanilla. Heat over medium heat until just warm.
3. Slowly pour a small amount of the warm milk into the egg mixture while whisking constantly to temper the yolks. Gradually add the rest of the milk.
4. Pour the entire mixture back into the saucepan. Cook over medium heat, whisking constantly, until it thickens and just begins to boil.
5. Let it boil for one full minute while whisking, then remove from heat.
6. Pass the custard through a sieve into a clean bowl to remove any lumps. Cover with plastic wrap, pressing it directly onto the surface to prevent a skin from forming. Allow to cool at room temperature. Do not refrigerate.

Make the Crème Mousseline:

1. Ensure the butter and pastry cream are both at room temperature.
2. In a stand mixer fitted with the paddle attachment, beat the butter on high speed until pale and fluffy, about 3 minutes.
3. Add the room-temperature pastry cream one tablespoon at a time, mixing on medium speed for 20 seconds between each addition.
4. Once all the pastry cream is incorporated, increase the speed to high and beat for an additional minute until light and smooth.
5. Use immediately to pipe or spread into molds, cake layers, or pastry shells before it firms up.

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Tips

• Ensure both the butter and pastry cream are at the same room temperature before combining to prevent splitting.
• Whisk constantly while cooking the pastry cream to avoid lumps.
• For a firmer texture, refrigerate the finished crème mousseline briefly before using.

Variations and Substitutions

• Add a tablespoon of liqueur (like Grand Marnier or Kirsch) for a flavor boost.
• Swap vanilla for almond or citrus zest for variation.
• Replace some of the butter with whipped cream for a lighter version (though it won’t be traditional mousseline).

FAQs

Can I make this ahead of time?
Yes, you can prepare the pastry cream a day in advance. Just bring it back to room temperature before using it to make the mousseline.

Why did my buttercream split?
This usually happens when the ingredients are not the same temperature. Make sure both butter and pastry cream are room temp.

Serving Suggestions

• Pipe into choux pastry or tart shells.
• Use as a filling for layered sponge cakes or genoise.
• Add as a creamy layer in verrines or trifle-style desserts.

Why You’ll Love This Recipe

• Luxuriously smooth and rich texture.
• Versatile for many classic French desserts.
• Perfect balance of sweetness and creaminess.
• Stable enough for piping and layering without being too heavy.