Vanilla Buttercream
Yield: approximately 6 cups, enough to frost two 6-inch cakes
Adapted from Miette (recipes from San Francisco's most charming pastry shop)
Note: This is a European-Style Buttercream, which is considerably different than American Buttercream (typically made from butter and powdered sugar). It is made with a base of egg whites, to which (cooked) sugar syrup and sweet butter is added. This frosting requires patience and diligence, but is well worth the effort. This buttercream is nothing short of lucious.
Ingredients
2 cups (14oz) sugar
1/3 c water
5 large egg whites, at room temperature
1 t cream of tartar
3 cups (1 1/2 pounds) unsalted butter, at room temperature
2 t vanilla extract
Instructions
Combine the egg whites and cream of tartar in the bowl of a stand mixer, fitted with a whisk attachment.
In a small saucepan over medium heat, combine the sugar and water. Clip a candy thermometer to the side of the pan. Cook the mixture until it reaches 240 degrees F, keeping a constant eye on it. (Boiling sugar syrup can cause a very bad burn if care is not taken.)
When the sugar syrup reaches 240 degrees F, whisk the egg whites on medium-low speed until soft peaks form.
When the syrup reaches 248 degrees F, reduce the speed to low and carefully drizzle the syrup into the mixer bowl (away from the whisk so that the sugar syrup does not splatter). When you have added all the syrup, raise the speed to high and beat until the mixture is cool to the touch (an instant-read thermometer should register between 65-70 degrees). The recipe states this can take 5-10 minutes. In my hand, it takes considerably longer. Whatever, the case, do NOT rush this step. You do not want to add the butter to warm meringue!
When the meringue is cool, begin adding the butter one tablespoon at a time -- waiting until each addition is incorporated before adding another. The mixture may deflate and begin to look curdled at this point. Raising the speed to high should alleviate this problem.
When all of the butter has been added, the frosting should be smooth and thick. Add the vanilla and mix to combine.
Use the buttercream immediately, or cover and refrigerate until needed.
Store in a zippered plastic bag for up to one week in the refrigerator, or up to 2 months in the freezer. (To thaw, leave in the refrigerator over night, not on the counter top.) To use buttercream that has been chilled, remove from the refrigerator and bring to room temperature. Transfer to a stand mixer fitted with a paddle attachment and beat until soft and spreadable, 2-3 minutes.
This frosting holds up well to piping and is extremely easy to spread. A cake decorators dream, really.