Preheat oven to 350˚F and assemble ingredients. Line muffin tins with parchment or paper cups.
Combine the flour and baking powder.
In a small bowl, lightly beat the egg whites till slightly foamy.
In a separate bowl, beat the butter and vanilla on medium speed until smooth and creamy. Gradually add in the sugar till incorporated. Turn to high speed and beat for 2 minutes scraping the side.
On low speed, add egg whites a small amount at a time, allowing to incorporate after each addition.
Using low speed, alternate adding the flour and milk until finished and just combined. Add in oil and mix just to incorporate.
Fill cupcake tins ⅔ full of batter. Bake for 15 to 20 minutes. Check for doneness every 2 minutes once it reaches the 15 minute mark.
Cool completely. Once cooled scoop out a hole in the middle of each cupcake. At this point you can freeze the cupcakes to make frosting easier.