3 cups (15 oz.) unbleached, all-purpose flour
1 tbsp. baking powder
1 tsp. salt
2 cups (14 oz.) granulated sugar
1 cup (8 oz.) unsalted butter, at room temperature
2 large eggs plus 4 large egg yolks, at room temperature
1 cup sour cream
1 tbsp. vanilla extract
Preheat the oven to 350˚ F. Line cupcake pans with paper liners. In a medium bowl, combine the flour, baking powder and salt. Whisk to blend. In the bowl of an electric mixer, combine the sugar and butter. Beat on medium-high speed until light and fluffy, about 3-4 minutes.
Blend in the eggs and egg yolks one at a time, scraping down the sides of the bowl as needed. In a small bowl or measuring cup, blend together the sour cream and vanilla. With the mixer on low speed, add the dry ingredients in three additions alternately with the sour cream, beginning and ending with the dry ingredients, and mixing each addition just until incorporated.
Divide the batter evenly between the prepared liners. Bake until the cupcakes are just set and pale golden, about 20-22 minutes. Let cool in the pan about 5 minutes, then remove to a wire rack to cool completely. Once cool, frost as desired.