Unsalted butter, room temperature • White sugar • Eggs, room temperature • Egg yolks, room temperature • Oil • Vanilla extract • Cake flour *see below* • Salt • Baking powder • Baking soda • Buttermilk, room temperature (can also do half sour cream and half milk, milk curdled with a 1/4tsp lemon juice or vinegar, or I've used creamline milk that has soured) • All purpose flour **if not using cake flour •