Day 4: Vanilla Vanilla Cupcakes

Another recipe from the Cupcakes book.
The conundrum: vanilla vanilla.  Classic, and boring.
I really liked this cake.  It's a really nice brand of vanilla.  I'd kind of like to substitute some other type of flour, like some cake flour with a bit of corn meal, just to make an interesting flavor/texture.  This, however, is a wonderful basic vanilla cake recipe. 

Makes 12 cupcakes

Ingredients:

For the cupcakes

• 1 1/4 cups flour
• 1 1/2 teaspoons baking powder
• 1/4 teaspoon salt
• 6 tablespoons unsalted butter, at room temperature
• 3/4 cup sugar
• 1 large egg, at room temperature
• 1 large egg white, at room temperature
• 1 teaspoon vanilla extract
• 1/2 cup whole milk

For the buttercream frosting

• 3 large egg whites, at room temperature
• 3/4 cup sugar
• Pinch salt
• 8 ounces (2 sticks) unsalted butter at room temperature, cut into 16 pieces
• Seeds from 1/2 vanilla bean
• 1 teaspoon vanilla extract
• Colored decorating sugars or nonpareils, for garnish (optional)

Directions:

For the cupcakes: Position a rack in the middle of the oven; preheat to 350 degrees. Line a standard 12-cup muffin pan with paper or foil cupcake liners.
Whisk together the flour, baking powder and salt in a medium bowl.
Combine the butter and sugar in the bowl of a stand mixer or hand-held electric mixer; beat on medium-high speed for 2 to 3 minutes, until light and fluffy.
Reduce the speed to low; add the egg and egg white separately, beating well after each addition. Add the vanilla extract and beat on low speed to incorporate. Stop to scrape down the bowl as needed.
Add the flour mixture in 3 additions, beating on low speed until just combined and alternating with several additions of milk; scrape down the sides of the bowl as needed. Increase the speed to medium-high and beat for about 30 seconds or just until no traces of flour remain. Do not overbeat.
Divide the batter evenly among the cupcake liners, filling each about three-fourths full. Bake for 18 to 20 minutes, until they are lightly golden and a toothpick inserted into the center of a cupcake comes out clean. Let the cupcakes cool in the pan on a wire rack for 5 minutes, then transfer the cupcakes to the wire rack and cool for 1 hour.
For the buttercream frosting: Combine the egg whites and sugar in a large heatproof bowl. Set the bowl over (but not touching) an inch or two of water in a large saucepan over medium heat.
Heat the mixture for about 2 minutes, whisking constantly, until the sugar has completely dissolved and the mixture is very warm to the touch (about 160 degrees on an instant-read thermometer). Remove the bowl from the saucepan.
Transfer to the bowl of a stand mixer or use a hand-held electric mixer to beat the egg white mixture on high speed for 6 minutes, until it is fluffy, has cooled to room temperature and holds stiff peaks. The mixture should not look dry.
Reduce the speed to medium-low; add the salt and then the butter, a few pieces at a time, beating well after each addition. If the frosting appears to separate or is very liquid after all the butter is added, increase the speed to high and beat for 3 to 5 minutes, until the frosting is smooth and creamy. Add the vanilla bean seeds and vanilla extract; beat until combined, scraping down the sides of the bowl as needed. Use right away.
Frost the cupcakes with the buttercream. Garnish the cupcakes with the colored sugars or nonpareils, if using.