Stable Swiss Meringue Buttercream
A reliable buttercream acts as the structural foundation for any decorated cake. By moving away from powdered sugar bases and toward a cooked meringue method, you gain control over sweetness and stability.
Temperature is the only variable that matters here.
If your butter is too cold, the emulsion will break and look curdled. If it is too warm, the frosting will turn into a greasy soup.
- stand mixer with whisk attachment
- heat-proof mixing bowl
- saucepan
- thermometer
What goes in.
- 5large egg whites
- 1.5 cupsgranulated sugar
- 2 cupsunsalted butter, cubed and softened to room temperature
- 1 tspvanilla bean paste
- 1 pinchfine sea salt
Finding the sweet spot
Add butter one cube at a time, waiting for each to fully incorporate before adding the next. If the mixture looks like scrambled eggs, keep whipping—the friction will eventually bring the temperature into alignment and smooth it out.
The method.
Heat the base
Whisk egg whites and sugar in a heat-proof bowl over a saucepan of simmering water. Do not let the bowl touch the water. Stir constantly until the sugar is fully dissolved and the mixture reaches 160°F.
Whip the meringue
Transfer to the stand mixer. Whisk on high speed until the bowl feels cool to the touch and the meringue forms stiff, glossy peaks that stand upright when the whisk is lifted.
Add the butter
Reduce speed to medium-low. Add cubed butter one piece at a time. The mixture may look soupy or curdled midway through; stay patient and keep the mixer running.
Finish the texture
Once all butter is added, increase speed to medium-high for 30 seconds to pull the emulsion together. Add salt and vanilla, then switch to a paddle attachment on low speed to beat out any air bubbles for a smooth finish.
Other turns to take.
Chocolate Buttercream
Fold in 6 ounces of melted, cooled semi-sweet chocolate after the final emulsion stage.
Fruit Infused
Replace 1/4 cup of the butter with an equal amount of strained, concentrated fruit puree.
When it doesn't go to plan.
Wipe your bowl with a paper towel and a splash of vinegar before starting to ensure there is zero grease, which prevents meringue from rising.
If your kitchen is very warm, place the bowl in the refrigerator for 10 minutes if the mixture refuses to thicken.
Butter should be soft enough to press a finger through, but still hold its shape; if it is greasy or oily, it is too warm.
The ones that keep coming up.
Why did my frosting turn into a runny mess?
The butter was likely too warm. Chill the bowl for 15 minutes, then continue whipping on high speed to re-emulsify.
Can I make this ahead of time?
Yes. Keep it in an airtight container in the refrigerator for up to a week. Bring it back to room temperature and re-whip until smooth before using.
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