In a bowl, whisk together flour, baking powder,baking soda, and salt together. Set aside.
Ina large bowl, using a mixer, beat the butter until smooth. Mix in sugar andbeat until creamy. Add vanilla extract.
Separate the egg yolks and egg whites. Mix in only egg whites to the sugar bowl.
Mix in flour mixture ½ cup at a time. Mix in sour cream and milk.
Scoop batter 2/3 full into cupcake liners. Bake for 20minutes. Let cool before decorating.