INGREDIENTS
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Nonstick baking spray with flour
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2 cups all-purpose flour
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2 cups granulated sugar
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1 cup unsweetened cocoa powder
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2 teaspoons baking soda
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1 1/4 teaspoons baking powder
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1 teaspoon kosher salt
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3 large eggs
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1 cup buttermilk
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1/2 cup warm water
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1 stick unsalted melted butter, cooled
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2 teaspoons pure vanilla extract
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1 stick unsalted butter
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4 ounces semisweet chocolate, chopped
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1/4 cup unsweetened cocoa powder
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2 teaspoons vanilla extract
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3 cups confectioners' sugar
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2/3 cup sour cream