– Cake flour – Butter – Vegetable oil – Sugar – Eggs – Whole fat buttermilk – Vanilla extract (I use a mixture of pure vanilla extract and also this clear imitation vanilla because it gives a little of that cake mix flavor). – Baking powder – Baking soda – Salt
Step 1. Preheat oven to 350°. Step 2. Butter and flour 3 cake pans or one half-sheet pan (12x18). (You can use butter or cooking spray.)
Step 3. In a large measuring cup or a pourable mixing bowl, combine the buttermilk, eggs, egg yolks, and vanilla and beat with a fork. Set aside.
Step 4. Sift cake flour and place it in the bowl of a stand mixer or large bowl. Add baking soda, baking powder, salt, and sugar and use the mixer on low to blend for about 30 seconds.
Step 5. With the mixer running on low, add the butter, one piece at a time and then pour in the vegetable oil. Mix until the flour and butter start to clump together and appear pebbly, about 30 seconds after the vegetable oil has been added.
Step 6. Pour in a little more than half of the buttermilk-egg mixture and mix on the lowest speed until blended, about 10 seconds. Increase the speed to medium-high and mix until starting to appear light and fluffy, about 1 minute. Without turning off the mixer, add the remaining buttermilk mixture in a slow stream.
Step 7. Stop the mixer and scrape the sides and bottom of the bowl, then beat at medium-high speed for about 15 seconds until well-mixed.
Step 8. Pour batter evenly into the prepared cake pans.
Step 9. Bake the layers for 20-25 minutes. Keep an eye on them because you don't want to overcook. Layers are done when they turn light golden brown and are springy to the touch, and of course you can always check with a toothpick, which I recommend doing at 20 minutes.
Step 10. Remove the layers from the oven and cool on racks for 10 minutes. Run a knife around the edges, then flip layers out of the pans and onto a plate and peel off the parchment. Cover the wire racks with a sheet of parchment paper and then re-flip the layers from the plate back to the rack.