MAKES 12 CUPCAKES
2/3 cup whole fresh or frozen strawberries, thawed
11/2 cups all-purpose flour, sifted
1 tsp. baking powder
1/4 tsp. coarse salt
1/4 cup whole milk at room temperature
1 tsp. pure vanilla extract
1/2 cup (1 stick) unsalted butter at room temperature
1 cup granulated sugar
1 large egg at room temperature
2 large egg whites at room temperature
1/2 cup whole frozen strawberries, thawed
1 cup (2 sticks) unsalted butter, firm and slightly cold
Pinch of coarse salt
31/2 cups powdered sugar, sifted
1/2 tsp. pure vanilla extract
1. Make cupcakes: Preheat oven to 350°. Line a 12-cup muffin pan with cupcake liners; set aside.
2. Pulse strawberries in a small food processor until puréed. You should have about 1/3 cup of purée. Add a few more strawberries, if necessary, or save extra purée for frosting; set aside.
3. Whisk together flour, baking powder, and salt in a medium bowl; set aside. In a small bowl, mix together milk, vanilla, and strawberry purée; set aside.
4. Cream butter on medium-high speed of mixer until light and fluffy. Gradually add granulated sugar and continue to beat until well-combined and fluffy. Reduce mixer speed to medium and slowly add egg and egg whites until just blended.
5. Add half flour mixture, slowly, with mixer on low; mix until just blended. Add milk mixture; mix until just blended. Slowly add remaining flour mixture, scraping down sides of bowl with spatula, as necessary, until just blended.
6. Divide batter evenly among prepared muffin cups. Transfer muffin pan to oven and bake until cupcake tops are just dry to the touch, 22 to 25 minutes. Transfer muffin pan to a wire rack and let cupcakes cool completely in pan before icing.
7. Make frosting: Purée strawberries until smooth. Beat together butter and salt on medium speed of mixer until light and fluffy. Reduce mixer speed and slowly add powdered sugar; beat until well combined. Add vanilla and 3 tbsp. strawberry purée (save remainder for another use) and mix until just blended. Do not overmix or frosting will incorporate too much air. Frosting consistency should be dense and creamy, like ice cream.