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1
Preheat oven to 350F.
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2
Line standard muffin tins with paper liners.
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3
Whisk together 3 1/4 cups cake flour, the baking powder, and salt.
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4
Stir the vanilla into the milk to combine.
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5
With an electric mixer on medium-high speed, cream butter until smooth.
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6
Adding the sugar in a steady stream, beat until pale and fluffy.
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7
Reduce speed to low.
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8
Add flour mixture in three batches, alternating with two additions of milk mixture, and beating until just combined after each.
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9
In another bowl, with an electric mixer on medium speed, whisk the egg whites until stiff peaks form (do not overmix).
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10
Fold one-third of the egg whites into the batter to lighten.
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11
Gently fold in the remaining whites until just combined.
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12
Toss chocolate chips with remaining tablespoon cake flour, and gently fold into batter.
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13
Divide batter evenly among lined cups, filling each three-quarters full.
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14
Bake, rotating tins halfway through, until a cake tester inserted in centers comes out clean and the tops are springy to the touch, about 22 minutes.
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15
Transfer tins to wire racks to cool completely before removing cupcakes.
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16
Cupcakes can be stored overnight at room temperature, or frozen up to 2 months, in airtight containers.
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17
To finish, use a small offset spatula to spread cupcakes with frosting.
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18
Refrigerate up to 3 days in airtight containers; bring to room temperature and, if desired, decorate with sprinkles before serving.
