Beat cream cheese and butter until well blended.
Add sugar, egg,egg whites and vanilla and blend until well blended.
Stir flour, baking powder and salt together in medium bowl.
Add flour mixture and buttermilk alternately and beat between after each addition, scraping sides of bowl.
After all ingredients are well blended, beat at medium speed for one minutes.
Add blueberries and gently fold in.
Fill muffin cups ⅔-3/4 full and bake at 350 for 18-20 minutes. Remove to wire rack when a finger touched lightly on top of cupcake does not leave an indentation.
When completely cool, frost with cream cheese frosting.