Banana Cupcakes With Peanut Butter Buttercream -- And Cinnamon Cupcakes

Ingredients

3/4 cup sugar
1/3 cup plus 2 tablespoons vegetable oil (recipe calls for grapeseed oil, but I didn't have any)
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 teaspoon cinnamon (optional, my addition)
1/2 teaspoon kosher salt
1 banana, mashed with a fork (use 1 1/2 bananas if not leaving any plain, and whisk into wet ingredients)
Handful of mini chocolate chips (optional, my addition)
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
Preparation
 
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 egg, egg yolk, buttermilk, and vanilla.
 
In another bowl, sift together the flour, baking soda, cinnamon, and salt. Using a whisk, mix the dry ingredients into the wet ingredients until just combined.
 
Divide slightly more than half of the batter evenly among six muffin cups, filling them three-quarters full.
 
Whisk the banana into the leftover batter and then stir in the chocolate chips. Divide the rest of the batter among the remaining six muffin cups.
 
Bake, rotating the tin halfway through, until a cake tester (or toothpick) inserted in the center of a cupcake comes out clean, about 15 to 18 minutes. The cinnamon cupcakes may be done first, so remove them as soon as they are. Leave the banana cupcakes to bake about 2 minutes longer, or until cake tester comes out clean. Invert the cupcakes onto a wire rack, turn them top side up and let them cool completely.
 
Meanwhile, 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, one piece 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 (or heap) the buttercream on top of the  banana cupcakes (and the cinnamon ones too if you like).
 
The cupcakes can be kept in an airtight container in the refrigerator for up to 3 days.

-Delicious Dishings