Banana Cupcakes with Peanut Butter Buttercream

A warm, toasted peanut butter and banana sandwich is quite possibly my favorite food. It's not one of those foods that I'd remember to say if someone asked what my favorite food was, but every time I have one I am reminded of what a perfect combination of ingredients it is. So naturally, when I saw the recipe for banana cupcakes with peanut butter buttercream I felt as if Karen DeMasco was reading my mind. I've got a feeling she's a pb&b lover too, why else would she decide the only thing more perfect than this combination in sandwich form is the same thing in cupcake form? Pure genius. The recipe itself is extremely easy, my only complaint is that because I don't have a stand mixer I had to do all of the long mixing by hand. That's nothing against the recipe though. I often find that I have 2 over-ripened bananas but not 4 (as a lot of breads call for), so this recipe is ideal for a quick fix for leftover bananas.

Banana Cupcakes with Peanut Butter Buttercream
Recipe from Karen DeMasco's The Craft of Baking 
Makes 1 dozen

Ingredients
3/4 cup sugar
1/3 cup plus 2 tablespoons grapeseed oil
3/4 cup mashed banana (about 1/2 medium bananas, mashed with a fork)
1 large egg
1 large egg yolk
1/3 cup plus 2 tablespoons buttermilk
3/4 teaspoon pure vanilla extract
1 cup plus 2 tablespoons unbleached all-purpose flour
3/4 teaspoon baking soda
1/2 teaspoon kosher salt

 Buttercream
2 large egg whites (1/4 cup)
1/4 cup sugar
8 tablespoons (1 stick) unsalted butter, cut into small pieces, at room temperature
1/4 cup creamy peanut butter
1/4 teaspoon pure vanilla extract
1/4 teaspoon kosher salt

Preheat the oven to 350 degrees. Line a standard 12-cup muffin tin with paper liners.
In a medium bowl, whisk together the sugar and oil. Whisk in the banana, egg, egg yolk, buttermilk, and vanilla.
In another bowl, sift together the flour, baking soda, and salt. Using a whisk, mix the flour mixture into the banana mixture until just combined. Divide the batter evenly among the muffin cups, filling them three-quarters full. Bake, rotating the tin halfway through, until a cake tester inserted in the center of a cupcake comes out clean, about 20 minutes. Invert the cupcakes onto a wire rack, turn them top side up and let them cool completely.
To make the buttercream, fill a medium saucepan with 2 inches of water and bring it to a simmer. In the bowl of an electric mixer, whisk together the egg whites and sugar. Set the bowl on top of the saucepan, and whisking constantly, heat the egg mixture until it is warm to the touch, about 3 minutes. Transfer the bowl to the mixer fitted with the whisk attachment and whisk on medium speed until the whites become translucent and shiny and form a soft peak, about 5 minutes more.
With the machine running, add the butter, a cube at a time, and mix until combined. Increase the speed to medium-high and add the peanut butter, vanilla and salt. Scraping down the sides of the bowl as necessary, beat until the buttercream becomes shiny and creamy, about 10 minutes. (The buttercream can be refrigerated for 1 week of frozen for up to one month. Before using, bring it to room temperature and beat it for a few minutes until smooth.) Spread the buttercream over the tops of the cupcakes, swirling it decoratively.
The cupcakes can be kept in an airtight container in the refrigerator for up to 3 days.