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1
Preheat oven to 350 F. Grease two 9-inch round cake pans, and line the bottoms with parchment paper.
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2
In a large bowl, whisk the flour, baking powder, baking soda and salt. Set aside.
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3
In another bowl, whisk together the boiling water, chocolate and cocoa powder until smooth. Set aside.
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4
Beat butter and sugar on medium speed in the bowl of a standing mixer until light and fluffy. Beat in eggs, one at a time. Beat in sour cream and vanilla extract.
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5
Reduce the speed to low and beat in 1/3 of the flour mixture, followed by half of the chocolate mixture. Repeat with another 1/3 of the flour mixture and the remaining chocolate mixture. Beat in the remaining flour mixture until just incorporated.
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6
Divide the batter evenly into the two prepared pans, smoothing the surface with a spatula. Bake 20 to 25 minutes or until a toothpick inserted into the cake comes out clean.
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7
Place the cakes (in the pans) on a wire rack to cool some. Then, while still warm, invert the cakes onto a greased rack.
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8
When the cakes are still warm, smear the marmalade on top of one cake layer. Place the other cake layer on top, gently press down a little bit. Transfer the cake (on a wire rack) over to a sheet pan that you've lined with waxed paper.
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9
To prepare the chocolate glaze, place the chocolate, butter and corn syrup in a medium heatproof bowl over a pot of simmering water. Stir the mixture using a wooden spoon until melted and smooth, about 5 minutes.
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10
Pour the warm chocolate glaze on top of the cake. Using a metal offset spatula, gently smooth the glaze over the cake, allowing it to run down the sides to completely coat the cake. Patch any bare spots with the spatula and the icing that has dripped.
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11
Cool until the glaze is barely set, then transfer the cake to a serving plate and refrigerate until the glaze is completely set, at least 1 hour.
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12
Cover and refrigerate the cake. Sprinkle the chopped orange peels on top of the cake and leave out in room temperature for at least an hour prior to serving.
