Preheat the oven to 350 degrees F. Make sure an oven rack is positioned in the middle of the oven. Line a 12-cup muffin tin with paper liners.
Whisk together the flour, sugar, baking powder, and salt in a large bowl (or in the bowl of an electric stand mixer). Add the butter, sour cream, egg, egg yolks and vanilla. Beat at medium speed until the batter is smooth and creamy, about 30 seconds to 1 minute. Scrape down the sides of the bowl with a rubber spatula and mix for a few more seconds, if needed, until no more dry pockets of flour remain. The batter will be thick - don't be alarmed!
Divide the batter evenly among the prepared muffin cups. Bake for 18-22 minutes (adding time, if needed) until the tops of the cupcakes spring back to the touch and a toothpick inserted in the center comes out clean. As always, don't overbake or the cupcakes will be dry.
Gently lift out the cupcakes from the muffin tin onto a cooling rack to let cool completely. Frost as desired!