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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.
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In a medium bowl, whisk together flour, baking powder, and salt; set aside.
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In a small bowl, mix together milk, vanilla, and strawberry puree; set aside.
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In the bowl of an electric mixer fitted with the paddle attachment, cream butter on medium-high speed, until light and fluffy. Gradually add sugar and continue to beat until well combined and fluffy.
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Reduce the mixer speed to medium and slowly add egg and egg whites until just blended.
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With the mixer on low, slowly add half the flour mixture; mix until just blended.
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Add the milk mixture; mix until just blended.
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Slowly add remaining flour mixture, scraping down sides of the bowl with a spatula, as necessary, until just blended.
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Divide batter evenly among prepared muffin cups. Transfer muffin tin to oven and bake until tops are just dry to the touch, 22 to 25 minutes. Transfer muffin tin to a wire rack and let cupcakes cool completely in tin before icing.
NOW FOR THE ICING:
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In the bowl of an electric mixer fitted with the paddle attachment, beat together butter and salt on medium speed until light and fluffy.
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Reduce mixer speed and slowly add confectioners' sugar; beat until well combined.
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Add vanilla and 3 tablespoons strawberry puree
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Mix until just blended. Do not overmix or frosting will incorporate too much air. Frosting consistency should be dense and creamy, like ice cream.
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They didn't taste exactly like the ones at the store, but they were really good.
Click here for a printable recipe and the list of ingredients needed.