INGREDIENTS
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all-purpose flour
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unsweetened cocoa powder
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(packed) brown sugar
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baking powder
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baking soda
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kosher salt
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large eggs, separated
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buttermilk
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olive oil
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vanilla extract
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oz. bittersweet chocolate (at least 70% cacao), finely chopped
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Nonstick vegetable oil spray
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Unsalted butter and warm pure maple syrup (for serving)