Bring cold ingredients to room temperature. Butter should be soft enough to hold a thumb-print but still keep its shape.

In a large bowl, using an electric mixer, best butter and sugar on high until light and fluffy, about 6 minutes.

Beat in eggs and egg yolks, one at a time, until combined. Beat in vanilla extract.

in another bowl, wish together flour, baking powder and salt.

With mixer on low, add 1/3 the flour mixture to butter mixture, beating to combine.

Beat in 3/4 cup buttermilk, another 1/3 flour mixture, another 3/4 cup buttermilk, and remaining flour mixture until just combined. Scrape down bowl as needed.

Makes 8 cups.