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1
Preheat the oven to 350F.
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2
Line two standard 12-cup muffin pans with paper liners.
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3
Into the bowl of an electric mixer, sift together flour, cocoa, sugar, baking soda, baking powder, and salt.
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4
Attach bowl to mixer fitted with the paddle attachment; add the eggs and yolk, the milk, oil, vanilla, and warm water.
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5
Beat on low speed until smooth and combined, about 3 minutes; scrape down the sides of the bowl as needed.
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6
Divide batter evenly among the muffin cups, filling each about two-thirds full.
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7
Bake, rotating pans halfway through, until a cake tester inserted in the center of a cupcake comes out clean, 20 to 25 minutes.
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8
Transfer pans to a wire rack to cool slightly.
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9
Invert cupcakes onto the rack; then reinvert and let them cool completely, top sides up.
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10
Frost cupcakes with Swiss Meringue Buttercream, swirling to cover, and garnish with Chocolate Curls.
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11
Cupcakes can be refrigerated in an airtight container for up to 3 days.
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12
Coat two 8-by-2-inch round cake pans with nonstick cooking spray.
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13
Line bottoms with parchment paper; spray parchment.
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14
Set aside.
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15
Follow instructions for One-Bowl Chocolate Cupcakes, dividing batter between the prepared pans.
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16
Bake, rotating pans halfway through, until a cake tester inserted in the centers comes out clean, about 45 minutes.
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17
Transfer pans to a wire rack to cool 30 minutes.
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18
Invert cakes onto the rack; peel off the parchment.
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19
Reinvert cakes, and let them cool completely, top sides up.
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20
Using a serrated knife, trim the tops of the cake layers to make level.
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21
Place one layer on a cake plate, and spread 2/3 cup buttercream on top.
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22
Place other cake layer on top.
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23
Spread entire cake with remaining buttercream, swirling to cover completely.
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24
Butter a 13-by-9-inch pan and dust with cocoa powder, tapping out excess.
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25
Follow instructions for One-Bowl Chocolate Cupcakes, transferring batter to the prepared pan.
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26
Bake, rotating pan halfway through, until a cake tester inserted in the center comes out clean, 45 to 50 minutes.
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27
Frost as desired.