Preheat oven to 350'.
Using cupcake liners, place 12 liners in a muffin pan and set to the side.
In a medium bowl, combine flour, baking powder and salt and set a side.
In a food processor or blender add strawberries and process until pureed.
Empty pureed strawberries into a 1/3c measuring cup and set aside. Add rest of strawberry puree to a small bowl and set aside to use in the frosting.
Using a electric mixer with bowl, cream butter on medium high speed until lightly fluffy.
Gradually add sugar and continue to mix until well blended. Reduce speed to low and slowly add one egg and egg whites and mix until lightly blended.
Add vanilla extract if using.
Mix together milk and 1/3c strawberry puree.
Alternate flour and milk mixture to mixer slowly ending with flour. Scrap down sides of bowl and continue to blend well.
Using a ice cream scoop or tablespoon, add batter to prepared muffin cups.
Bake for 20 to 25 minutes, or until lightly browned.
Cool cupcakes completely on a wire rack before adding the frosting.