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Preheat the oven to 375F. Line a 12-cup or 2 6-cup muffin tins with paper liners.
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In a large bowl, sift together flour, baking powder, and salt; set aside.
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In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar on medium speed until fluffy, about 3 minutes. Add egg, egg yolks, and vanilla; mix until well combined. Reduce speed to low; alternate adding reserved flour mixture and milk to mixer, beginning and ending with flour. Remove bowl from mixer; gently fold in berries by hand.
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Divide batter among muffin tins. Bake until light golden, about 40 minutes for large muffins, about 25 minutes for small muffins. Cool in pan 15 minutes. Remove from pan; transfer to wire rack, and let cool completely.