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1
Place rack in center of oven and preheat oven to 350 degrees F.
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2
Place a cupcake liner into each section of an 8-cupcake tin.
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3
Whisk together flours, cocoa, baking soda and salt in a medium bowl and reserve.
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4
Combine sour cream and buttermilk in a small bowl and reserve.
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5
Combine butter, oil and brown sugar in the bowl of a stand mixer and mix on high speed, scraping down sides of bowl, until sugar has dissolved and mixture is light in color, about 1 minute.
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6
Add egg and egg white and beat an additional 1 minute.
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7
Add 1/3 of flour-cocoa mixture, then 1/3 sour cream buttermilk mixture, mixing well after each addition.
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8
Repeat with remaining dry and wet ingredients.
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9
Distribute batter evenly among 8 cupcake tins.
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10
Bake for 15 to 17 minutes, or until a toothpick inserted into cupcake comes out clean.
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11
Let cupcakes cool slightly, transfer to wire racks and cool completely, 10 to15 minutes.
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12
Combine confectioners' sugar and milk in a small saucepan and heat over low heat until sugar is dissolved.
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13
Add chocolate and stir until melted and icing is the consistency of thick pancake batter; add more milk if necessary.
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14
While still warm, top each cupcake with 1 1/2 to 2 teaspoons icing.
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15
Let icing harden completely, about 10 minutes.
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16
Place cream cheese in a small microwave-save bowl and microwave on high for approximately 10 to 15 seconds, until cream cheese is melted but before it begins to bubble.
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17
Add confectioners' sugar and stir until sugar is dissolved.
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18
Let mixture cool slightly and transfer to a small plastic bag.
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19
Snip just the very bottom corner of the bag, then force icing to bottom of bag.
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20
Pipe a squiggle of icing down the center of each cupcake.
