90 g egg whites (about 3 egg whites)
A pinch of cream of tartar
A pinch of salt
175 g granulated sugar
¼ cup water
2 sticks (8 ounces) butter at room temperature
1 tablespoon Cointreau, Myers’s Dark Rum or vanilla extract
In a small saucepan, heat the sugar and water until boiling. Use a pastry brush and cold water to brush any sugar from the side of the pan. Clip a candy thermometer to the side of the pan and cook until reaching 240°F.
While the sugar cooks beat the egg whites. Begin at low to medium speed until they are foamy. Then add the cream of tartar and salt. Increase the speed of the mixer to high and beat until soft peaks form.
With the mixer on low, slowly pour the hot sugar syrup between the side of the bowl and the whisk. Once all the syrup is incorporated, raise the mixer to high and beat until the bottom of the mixing bowl is cool to the touch.
At this point you have an Italian meringue. It is time to incorporate the butter. Pinch off pieces of butter and toss them into the meringue a few at a time. The butter should be soft and feel a little greasy. Once the pieces of butter have disappeared into the meringue toss in a few more pieces. Continue until all the butter is incorporated. Beat in the Cointreau. The buttercream should be silky smooth.
Use on strawberry cupcakes.