Add strawberries to the bowl of a food processor (include the strawberries from the frosting if using).  Puree until smooth.  Measure out 1/3 cup and set aside.

In a medium bowl, whisk together the flour, baking powder and salt and set aside.

In a small bowl, mix together the milk, vanilla and 1/3 cup strawberry puree.  Set aside

In the bowl of a stand mixer, add the butter and cream on medium-high until light and fluffy.  Add the sugar and beat until combined.  Turn down the mixer speed and add the egg and egg whites slowly.  Beat until just combined.

With the mixer on low, add half of the flour mixture to the butter mixture.  Mix until just incorporated.  Add the milk and strawberry mixture and mix until just blended.  Scrape down the sides and slowly add the remaining flour.  Mix just until incorporated.

Divide evenly among the lined muffin cups.  Bake for 22-25 minutes, or until a toothpick inserted comes out clean.  Cool completely before icing.

In the bowl of an electric mixer fitted with the paddle attachment, beat the butter until light and fluffy.  Add the cream cheese and beat on medium until light and fluffy.  Reduce the speed and slowly add the confectioners sugar.  Beat until well combined.  Add the vanilla and 3 tablespoons of strawberry puree.  Mix until just blended.  Place in the refrigerator until you are ready to frost the cupcakes.