Vanilla Cupcakes

INGREDIENTS

• :
• 1½ cups all-purpose flour
• 1 cup granulated sugar
• 1½ teaspoons baking powder
• ½ teaspoon table salt
• 8 tablespoons unsalted butter (1 stick), room temperature
• ½ cup sour cream
• 1 large egg , room temperature
• 2 large egg yolks , room temperature
• 1½ teaspoons vanilla extract
• 1 cup (8 ounces) unsalted butter, at room temperature
• 2½ cups powdered sugar
• 1 tablespoon vanilla extract