01For the strawberry cupcakes, preheat oven to 350 F. Line 12-cup muffin tin with cupcake liners. Add 2/3 cup strawberries in food processor, and blend until smooth. Strawberry puree should yield 1/3 cup.
02Whisk together flour, baking powder, and salt in large bowl. Mix together milk vanilla, and strawberry puree in separate bowl; set aside.
03Beat butter and sugar in bowl of stand mixer fitted with a paddle attachment on medium-high speed until light and fluffy, about 5 minutes. Reduce speed to medium, and slowly add eggs, and egg whites until just combined. With the mixer running, add half flour mixture, until just combined. Add milk mixture and food coloring. Slowly add remaining flour mixture, stopping, and scraping down the sides as needed, until fully combined.
04Divided batter among prepared muffin tin. Bake until tops are dry, and toothpick inserted into the center comes out clean, about 20 to 25 minutes. Let cupcakes cool completely before icing.
05For the champagne buttercream, add cream cheese, butter, sugar, champagne, vanilla, and salt in bowl of stand mixer fitted with paddle attachment. Beat on medium speed until light and fluffy, about 8 to 10 minutes.
06Transfer to piping bag fitted with large star tip. Pipe icing onto each cupcake. Garnish cupcakes with strawberries and serve.