Swiss Meringue Buttercream Frosting

• portions: 4 cups

Ingrédients

1 cup plus 2 Tbsp. (225 g) granulated sugar

5 (135 g) large egg whites

½ cup (65 g) powdered sugar

1 cup plus 5 Tbsp. (300 g) unsalted butter, cut into pieces, room temperature

1 tsp. vanilla extract

½ tsp. kosher salt

1 vanilla bean, split lengthwise; 5½ oz. bittersweet chocolate, melted, cooled but still liquid; or 3 Tbsp. espresso, cooled

Instructions

Combine granulated sugar and egg whites in the bowl of a stand mixer and set over a medium saucepan filled with 1" of gently simmering water (do not let bowl touch water). Heat, whisking constantly, until sugar is dissolved and an instant-read thermometer registers 115°, about 5 minutes.

Fit bowl onto stand mixer fitted with whisk attachment and beat on medium-high speed until meringue is stiff, glossy, and dense, about 5 minutes. Turn off mixer, add powdered sugar, and mix on low speed until incorporated. Increase speed to medium-high and beat until the bowl is cool to the touch, about 2 minutes.

With the motor running, add butter a piece at a time, incorporating fully before adding the next piece, 8–10 minutes. If mixture starts to look chunky or liquidy, just keep beating; it will come back together. Scrape down the sides of the bowl and add vanilla extract and salt. Beat until buttercream looks glossy and smooth. Scrape in vanilla seeds (discard pod) or add chocolate or espresso, depending on desired flavor. Beat until smooth.

Do Ahead: Buttercream can be made 3 days ahead. Cover and chill. Bring to room temperature, then beat until smooth before using.