To celebrate my nephew turning one year old the other weekend, I made cupcakes (not that I really needed an excuse to make something sweet). I used a basic vanilla cake recipe and topped the cupcakes – both regular and mini-sized ones – with a blueberry buttercream frosting.
I borrowed the frosting recipe from Miette. It is as follows:
- 5 cups (14 ounces) sugar
- 1/2 cup water
- 5 large egg whites
- 1 teaspoon cream of tartar
- 3 cups (1 1/2 pounds) unsalted butter, at room temperature
- 2 tablespoons vanilla extract
1. In a small saucepan over medium heat, combine the sugar and water. Clip a candy thermometer to the side of the pan. Cook hte mixture until it reaches 248 degrees F, 5 to 10 minutes, keeping a constant eye on it.
2. Meanwhile, combine the egg whites and cream of tartar in the bowl of a stand mixer fitted with the whisk attachment. When the sugar syrup reaches 240 degrees F, whist the egg whites on medium-low speed until soft peaks form. Slowly pour in the syrup, raise the speed to high, and whisk until stiff peaks form.
3. When the sugar syrup reaches 248 degrees F, reduce the speed to low and very carefully drizzle the syrup into the mixer bowl, away from the whisk so the hot syrup doesn’t spatter. Be careful because the syrup is very hot. When you have added all of the syrup, raise the speed to high and beat until the mixture is cool to the touch (an instant-read thermometer should register 65 to 70 degrees F), 5 to 10 minutes.
4. Only when the meringue is cool enough should you begin add the butter. Reduce the speed to medium. With the mixer running, drop in the butter, 1 tablespoon at a time, waiting until each is incorporated before adding another. The mixture may deflate and begin to look curdled. Raise the speed to high and continue to add tablespoon-size pieces of butter, making sure each is completely combined before adding more. When all of the butter has been added, the frosting should be smooth and thick. Add the vanilla and mix to combine.
5. For each 1 cup of vanilla buttercream, stir in 3 tablespoons of blueberry juice until well combined and smooth. I like blueberries, so I may have added more than 3 tablespoons. To make blueberry juice, in a saucepan over medium-low heat, combine 2 cups of fresh blueberries, 2 tablespoons of water, and 1 tablespoon sugar. Cook, gently stirring the berries to help them break down, until the berries are liquefied, 10 to 15 minutes. Remove from the heat and strain into a heatproof bowl through a fine-mesh sieve. Let cool to room temperature before adding to the buttercream.