For the Cupcakes:
10 ounces frozen whole strawberries (2 cups)
3/4 cup whole milk, room temperature
6 large egg whites, room temperature
2 teaspoons vanilla extract
2 1/4 cups (9 ounces) cake flour
1 3/4 cups (12 1/4 ounces) granulated sugar
4 teaspoons baking powder
1 teaspoon salt
12 tablespoons unsalted butter, cut into 12 pieces and softened
For the Frosting:
10 tablespoons unsalted butter, softened
2 1/4 cups (9 ounces) confectioners’ sugar
12 ounces cream cheese, cut into 12 pieces and softened
- For the cupcakes: Adjust oven rack to middle position and heat oven to 350 degrees. Line muffin pan with paper liners.
- Transfer strawberries to a large bowl, cover, and microwave until strawberries are soft and have released their juice, about 5 minutes. Place in fine-mesh strainer set over small saucepan. Firmly press fruit dry (juice should measure at least 3/4 cup); reserve strawberry solids. Bring juice to boil over medium-high heat and cook, stirring occasionally, until syrupy and reduced to 1/4 cup, 6 to 8 minutes. Whisk milk into juice until combined.
- Whisk strawberry milk, egg whites, and vanilla in bowl. Using stand mixer fitted with the paddle attachment, mix flour, sugar, baking powder, and salt on low speed until combined. Add butter, 1 piece at a time, and mix until only pea-size pieces remain, about 1 minute. Add half of milk mixture, increase speed to medium-high, and beat until light and fluffy, about 1 minute. Reduce speed to medium-low, add remaining milk mixture, and beat until incorporated, about 30 seconds. Give batter final stir by hand.
- Divide the batter evenly among muffin pan cups and bake until toothpick inserted in center comes out clean, 15 to 19 minutes. Transfer muffin pan to wire rack and let cool in the muffin pan 5 minutes, then transfer to a wire rack to cool completely.
- To make the Frosting: Using a stand mixer fitted with paddle attachment, mix butter and sugar on low speed until combined, about 30 seconds. Increase speed to medium-high and beat until pale and fluffy, about 2 minutes. Add cream cheese, one piece at a time, and beat until incorporated, about 1 minute. Add reserved strawberry solids and salt and mix until combined, about 30 seconds. Pipe frosting onto cooled cupcakes.