- Preheat oven to 350°F. Line muffin tins with paper liners.
- Place strawberries in a small food processor; process until pureed. You should have about 1/3 cup of puree, add a few more strawberries if necessary or save any extra puree for frosting; set aside.
- In a medium bowl, sift flour, baking powder, and salt
- In a small bowl, mix together milk, vanilla, and strawberry puree; set aside
- In electric mixer, cream butter on medium-high speed, until light and fluffy. Gradually add sugar and continue to beat until well combined and fluffy.
- Reduce the mixer speed to medium and slowly add egg and egg whites until just blended
- With the mixer on low, slowly add half the flour mixture; mix until just blended. Add the milk mixture; mix until just blended. Slowly add remaining flour mixture, scraping down sides of the bowl with a spatula, as necessary, until just blended.
- Fill each cupcake cup evenly with the batter.
- Bake for about 22-25 minutes or until cake tester comes out clean.
- Allow cupcakes to cool completely before frosting.