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1
Preheat oven to 350 degrees F.
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2
Use 1 tablespoon of butter to grease 3 (9-inch) cake pans.
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3
Line the bottom of each pan with a parchment paper round.
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4
Combine cocoa and chocolate in medium bowl.
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5
Pour boiling water over the chocolate mixture and whisk until smooth; reserve.
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6
Sift together the flours, baking soda, and salt into a medium bowl; reserve.
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7
Place the 3/4 pound butter in large bowl and beat with electric mixer at medium-high until creamy, about 1 minute.
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8
Add dark brown and granulated sugars and beat on high until light and fluffy, about 3 minutes.
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9
Stop mixer and scrape down bowl with rubber spatula.
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10
Add the eggs, 1 at a time, beating 30 seconds on medium-high after each addition.
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11
Reduce speed to medium and add sour cream and vanilla.
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Beat until combined.
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13
Stop mixer and scrape down bowl.
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14
With mixer on low add about 1/3 of flour mixture, followed by about 1/2 of chocolate mixture.
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15
Repeat ending with flour mixture, beating until just combined.
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16
Stop mixer and scrape down sides of bowl.
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17
Stir gently to thoroughly combine.
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Divide batter evenly among cake pans and smooth with spatula.
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19
Bake until skewer inserted in center comes out clean, about 25 minutes.
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20
Cool the cakes in their pans on wire racks for about 15 minutes.
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21
Invert cakes, 1 at a time, onto a large plate, peel off parchment, and invert onto rack.
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22
Cool completely before icing between layers, on sides, and on top with Vanilla Buttercream Icing.
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23
Serve at room temperature.
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24
(Any buttercream will not fare well in too warm conditions.)
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25
9 large egg yolks
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26
1 cup sugar
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27
1/2 cup plus 2 tablespoons light corn syrup
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28
1 1/4 pounds (5 sticks) unsalted butter, softened
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29
2 teaspoons pure vanilla extract
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30
In a large bowl beat the yolks with an electric mixer until light in color; reserve.
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31
Combine the sugar and corn syrup in a small saucepan (preferably nonstick) over medium heat, stirring constantly, until the sugar dissolves and syrup comes to a rolling boil.
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32
Transfer syrup to a heatproof bowl to stop cooking.
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Pour a small amount of the syrup into the yolks and begin beating with electric mixer.
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34
Pour the remaining corn syrup into the mixture in a steady stream.
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35
Continue beating until completely cool and fluffy, about 5 minutes.
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36
Gradually beat in the butter and vanilla until the icing is light and fluffy, about 3 minutes.
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37
Use immediately.
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38
(Or can be covered and refrigerated up to 5 days.)
