Preheat the oven to 350 degrees (180 degrees F). Place 6 cupcake liners in a muffin pan.
In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, baking powder, and salt.
Cut up the butter into small cubes and add to the dry ingredients. Mix on low speed until it resembles wet sand.
Add the oil, yogurt, milk, and vanilla, and mix until just combined.
In a separate bowl, whip the egg white to stiff peaks. Gently fold it into the batter with a rubber spatula until just combined.
Fill the cupcake liners about ⅔ of the way full.
Bake for 16-18 minutes or until a tooth pick inserted comes out clean.
Cool completely before frosting.