- 3⅓ cups cake flour
- 2 cups sugar
- 1 tablespoon baking powder
- 1 teaspoon kosher salt
- ½ teaspoon baking soda
- 1 cup (2 sticks) unsalted butter, room temperature
- 1 cup buttermilk, room temperature
- 2 tablespoons vegetable oil
- 7 large egg yolks
- 1 large egg
- 1 tablespoon vanilla extract
- Arrange racks in lower and upper thirds of oven; preheat to 400°. Line two standard 12-cup muffin tins with cupcake liners.
- Whisk flour, sugar, baking powder, salt, and baking soda in the bowl of a stand mixer fitted with the whisk attachment. Add butter, buttermilk, and oil and beat on medium speed, scraping down sides of bowl, until smooth.
- Whisk egg yolks, egg, and vanilla in a medium bowl until smooth. Add egg mixture to flour mixture in 2 additions, beating well between additions. Continue to beat on medium speed until mixture is homogenous and very thick, about 2 minutes.
- Divide batter evenly among muffin cups, filling two-thirds full (a level ⅓ cup batter per cupcake). Bake 5 minutes, then reduce oven temperature to 350°. Continue baking, rotating pans halfway through, until cupcakes have domed and spring back when touched in the center, 20–25 minutes. Transfer to a wire rack and let cool.