Preheat oven to 350°F. Spray three 6 inch pans with cooking spray and line bottom with parchment.
In a medium bowl mix together the flour, baking powder and salt. Set aside.
In the bowl of your stand mixer fitted with the paddle attachment, cream the butter and both sugars until they are fully combined and light and fluffy.
Add the egg whites, vanilla and vegetable oil and continue to mix on low until incorporated. Scrape the bowl as needed.
With the mixer still on low speed, alternate adding the dry ingredients and buttermilk. Start with adding about 1/3 of the dry ingredients, half the buttermilk and so on. Make sure to start and end with the dry ingredients.
Toss the mini chocolate chips with one tablespoon flour and then stir the coated mini chocolate chips into the batter. It's important to coat the chocolate chips with the flour since it keeps them from sinking to the bottom of the batter.
Divide the batter evenly between the three prepared pans.
Bake for 30-35 minutes or until a toothpick comes out clean.
Let the cakes cool in the pans for about 10 minutes and then transfer to a wire rack to cool completely.