Instructions

  1. In a large heatproof mixing bowl or the bowl of a stand mixer, whisk together (briefly) the sugar, egg whites, and salt.

  2. Place the bowl over a saucepan of simmering water (you should just barely see some lazy bubbles coming up), and whisk constantly until the mixture measures 161°F (71.7°C) on a digital thermometer.

  3. Remove the bowl from the heat, and beat the meringue with your mixer's whisk attachment until stiff.

  4. With the mixer running, add the butter a few tablespoons at a time. Make sure each portion of butter is completely incorporated before adding the next.

  5. Once half the butter is in, stop and scrape any sticky residue from the sides and bottom of the bowl. Whisk to combine, then finish adding the rest of the butter.

  6. Beat in the flavoring of your choice.

  7. If the frosting seems soft, chill for 15 minutes before using.

  8. Store for up to one week in the refrigerator, or six months in the freezer.

Tips from our Bakers

  • The classic flavor for this frosting is vanilla: add 1 teaspoon to 1 tablespoon vanilla extract or vanilla paste, to taste. Or try these flavors:

    -   For Coconut Swiss Buttercream: Add 1/2 teaspoon coconut flavoring and 1/2 cup coconut milk powder.
    -   For Chocolate Swiss Buttercream: Reserve 3/4 cup (6 ounces) of the butter from the recipe. Melt 1 cup (6 ounces) bittersweet chocolate and cool to room temperature. Combine the melted chocolate and the butter until mixed, then add this mixture to the frosting.
    -   For Raspberry Swiss Buttercream: Add 2 tablespoons raspberry purée, or simply mix a half pint of fresh raspberries into the finished frosting.
    -   For Lemon Swiss Buttercream: Add 1 tablespoon fresh grated lemon rind (zest) and 2 teaspoons fresh lemon juice. You can also substitute 1 tablespoon lemon juice powder for the zest and juice, adding it to the egg whites before beating.

  • To make a vegan version of this frosting: Replace the egg whites with 1/2 cup (113g) reduced aquafaba. To prepare the aquafaba, heat 1 cup (227g) aquafaba in a saucepan over medium heat until it's reduced by half. Be sure to let the mixture cool completely before using; it can be prepared a few days in advance if desired. Additionally, substitute 32 tablespoons (454g) unsalted vegan butter for the butter called for in the recipe. Our test kitchen prefers Earth Balance Vegan Buttery Sticks.