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1
For the Cake: Adjust oven rack to middle position and heat oven to 350F Grease 18 x 13 inch rimmed baking sheet.
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2
Combine flour, sugar, baking soda, and salt in large bowl.
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3
Whisk eggs and yolks, vanilla, and sour cream in another bowl until smooth.
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4
Heat chocolate, butter, oil, water, and cocoa in large saucepan over medium heat, stirring occasionally, until smooth, 3-5 minutes.
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5
Whisk chocolate mixture into flour mixture until incorporated.
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6
Whisk egg mixture into batter, then pour into prepared baking pan.
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7
Bake until toothpick inserted into center comes out clean, 18-20 minutes.
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8
Transfer to wire rack.
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9
For the Icing: About 5 minutes before cake is done, heat butter, cream, cocoa, and corn syrup in large saucepan over medium heat, stirring occasionally, until smooth.
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10
Off heat, whisk in confectioners'sugar and vanilla.
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11
Spread warm icing evenly over hot cake and sprinkle with pecans.
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12
Let cake cool to room temperature on wire rack, about 1 hour, then refrigerate until icing is set, about 1 hour longer.
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13
(Cake can be wrapped in plastic and refrigerated for up to 2 days.
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14
Bring to room temperature before serving).
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15
Cut into 3-inch squares.
