INGREDIENTS
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For the cake:
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3/4 cup dark unsweetened cocoa powder
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1 & 1/4 cups hot water
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2/3 cup sour cream
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2 & 2/3 cups all-purpose flour
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2 teaspoons baking powder
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1 teaspoon baking soda
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1/2 teaspoon salt
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3/4 cup unsalted butter, softened
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1/2 cup shortening
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1 & 1/2 cups granulated sugar
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1 cup firmly packed dark brown sugar
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3 large eggs, at room temperature
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1 tablespoon vanilla extract
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For the salted caramel:
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1/2 cup heavy cream
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1 teaspoon fleur de sel
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1 cup granulated sugar
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2 tablespoons light corn syrup
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1/4 cup sour cream
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For the whipped caramel ganache frosting:
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1 pound dark chocolate (60-70% cacao), chopped
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1 & 1/2 cups heavy cream
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1 cup granulated sugar
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2 tablespoons light corn syrup
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2 cups unsalted butter, soft but cool, cut into 1/2-inch pieces
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For assembling the cake:
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2 teaspoons fleur de sel, plus more for garnish