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1
Adjust oven rack to lower-middle position and heat oven to 350 degrees F. Generously grease the cake pans with butter and dust with flour.
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2
Whisk sugar, flour, cornstarch, baking soda, and salt in a large bowl; set aside.
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3
Place cocoa and coffee in a medium bowl.
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4
Whisk in 3/4 cup boiling water to form a smooth paste.
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5
Stir in sour cream and vanilla and set aside.
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6
With a hand mixer in a medium bowl, beat egg whites to soft peaks.
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7
Without cleaning beaters, mix melted butter into dry ingredients until mixture is smooth.
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8
Immediately add cocoa mixture, and beat until batter is smooth, 2 to 3 minutes.
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9
Carefully fold egg whites into batter until just incorporated.
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10
Divide batter evenly between pans and bake until a skewer inserted into center comes out with wet crumbs, 30 to 35 minutes.
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11
Remove from oven, and let cakes sit in pans to cool slightly, about 5 minutes.
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12
Invert each cake onto a plate, then onto a cooling rack and split each cake to make 4 layers.
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13
Frost with Chocolate Frosting and serve.
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14
Mix egg substitute or yolks, cocoa, coffee, vanilla, and salt in a small bowl with a whisk.
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15
Beat butter in a medium bowl with an electric mixer until light and fluffy.
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16
Add melted chocolate and cocoa mixture; continue to beat until smooth.
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17
Add confectioners' sugar, 1 cup at a time, beating slowly at first, until sugar has been incorporated into mixture, then at medium speed until frosting is light and fluffy.
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18
Add corn syrup, and beat until frosting is smooth and glossy.
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19
If frosting is still stiff, add droplets of milk until it is of spreading consistency.
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20
(Frosting can be refrigerated for up to 1 week and microwaved for a few seconds until just spreadable).
