- 18 ounces fresh raspberries
- 1 cup plus 6 tablespoons sugar
- 1 teaspoon cornstarch
- 1/2 cup water
- 4 large egg whites, at room temperature
- 1/4 teaspoon salt
- 2 1/2 sticks unsalted butter, cut into 20 pieces, at room temperature
- 1/2 teaspoon pure vanilla extract
Place 6 ounces raspberries and 2 tablespoons sugar in food processor and pulse until smooth. Strain into small saucepan and whisk in cornstarch. Bring to boil over medium-high heat, then simmer over medium-low until thickened and reduced to about 3 tablespoons, 4 to 5 minutes. Transfer to bowl and cool completely.
Stir remaining 1 1/4 cups sugar and water in heavy-bottomed medium saucepan over medium-low heat until sugar dissolves. Increase heat to medium-high and boil syrup until it registers 238-240°F on candy thermometer, 5 to 7 minutes.
While syrup boils, whip egg whites with whisk attachment on medium speed until soft peaks form, 2 to 3 minutes. When syrup reaches temperature, with mixer running on medium-high speed, slowly and carefully add it to egg whites. Beat until outside of bowl is cool to the touch and whites are thick and glossy, about 7 minutes.
With mixer on medium speed, add butter, one piece at a time. Beat until light and fluffy, 1 to 2 minutes. Add raspberry syrup and vanilla and mix until combined, about 30 seconds. Pick out 20 raspberries for garnish and fold in the remaining ones with a rubber spatula—it’s fine for them to be crushed.
Makes enough frosting for a 2 layer 9 inch cake or 24 cupcakes. From Serious Eats