Ingredients
Cupcakes
1 1/2 cups all-purpose flour
1 cup granulated sugar
1 1/2 teaspoons baking powder
1 teaspoon salt
8 tablespoons (1 stick) unsalted butter, at room temperature
1/2 cup sour cream
1 large egg, at room temperature
2 egg yolks, at room temperature
1 1/2 teaspoons vanilla extract
Vanilla Buttercream Frosting
1 cup unsalted butter, at room temperature
2 1/2 cups powdered sugar
1 tablespoon vanilla extract
Preparation
Adjust oven rack to middle position & preheat to 350°F. Line a muffin tin with paper liners.
Whisk together flour, sugar, baking powder, and salt in bowl of standing mixer fitted with paddle attachment. Add butter, sour cream, egg, egg yolks, and vanilla; beat at medium speed until smooth and satiny, about 30 seconds. Scrape down sides of bowl with rubber spatula and mix by hand until smooth and no flour pockets remain.
Divide batter evenly among cups of prepared tin. Bake until cupcake tops are pale gold and toothpick inserted into center comes out clean, 20-24 minutes. Remove the cupcakes from the pan and transfer to wire rack; cool cupcakes to room temperature before frosting.
To make the buttercream, using the wire whisk attachment of your stand mixer, whip the butter on medium-high speed for 5 minutes, stopping to scrape the bowl once or twice.
Reduce the speed to low and gradually add the powdered sugar. Once all of the powdered sugar is incorporated, increase the speed to medium-high and add the vanilla, mixing until incorporated. Whip at medium-high speed until light and fluffy, about 2 minutes, scraping the bowl as needed.
Pipe onto cupcakes and decorate as desired.
