• Preheat oven to 350 degrees. Line your cupcake baking sheet with paper cupcake liners.
• Whisk flour, baking powder, salt, and baking soda in a medium bowl until well blended.
• In another bowl, beat butter on medium-high for 30 seconds.
• Add sugar and vanilla to the butter, and beat until combined.
• Add egg whites and eggs, one at a time for the eggs, beating well after each one is added.
• Alternate the flour and buttermilk into the butter mixture, beating on low speed until everything is mixed together.
• Scoop the batter into the lined cupcake tins until they are 2/3 filled.
• Bake at 350° for 20-25 minutes or until a toothpick inserted in the center comes out clean.
• Remove pan from oven and allow cupcakes to cool for 10 minutes.
• Remove cupcakes from the cupcake tray and place on wire racks allowing to cool completely.
• Using a small spoon or a cupcake scoop, make a small hole in the center of each cupcake.  Take care to make sure the hole does not completely go through to the cupcake bottom.
• Fill the hole in the cupcake to the top of the baked and cooled cupcake with the blueberry filling.

Frosting Directions:

• Cream the butter and powder sugar until it looks light and creamy.  If it doesn't cream, add several drops of the heavy whipping cream until it creams.
• Test to see if the frosting can form and hold a stiff peak by taking a spoonful of frosting and turning the spoon upside down. If the frosting stays on the spoon, it is ready.  If not, then add more powder sugar and mix well until the frosting can make and hold a stiff peak.
• When the frosting is ready, scoop it into a pastry bag with a large tip.
• Twist the open end of the pastry bag to push the frosting to the #15 tip.
• Start by frosting on the outside edge of the cupcake working to the center of the cupcake.
• Enjoy!