Preheat your oven to 350°. Line 2 cupcake pans with cute little liners.
In a stand mixer, mix together all your dry ingredients for about one minute. Add your softened butter and oil, and mix on low speed until it’s the texture of wet sand and all the dry ingredients are coated in delicious fat.
Whisk together your eggs and yolks, vanilla, and sour cream. Add to the stand mixer and mix on medium speed until everything is just incorporated. About one minute. DO NOT JUST KEEP MIXING! We don’t want tough cupcakes.
Remove bowl from stand mixer and use a rubber spatula to make sure all the ingredients are well mixed. There might be tiny lumps, and that’s okay. This is bits of fat and it will all come together while baking. Trust me.
For regular sized cupcakes, fill a lined cupcake tin using a large (3 tbs) cupcake or ice cream scoop. This will fill each liner about ½-2/3 full.
Bake in a 350° oven for 20-22 minutes or until a toothpick inserted into the center comes back clean. Cool for 5 minutes in the pan, then remove to a cooking rack until completely cooled. If you have to have one unfrosted cupcake for, you know, quality control, I understand.