INGREDIENTS
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1 1/2 lb. green beans, halved crosswise
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kosher salt
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7 tbsp. unsalted butter, divided
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1 medium yellow onion, sliced into rings
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8 oz. button mushrooms, trimmed and sliced
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Black pepper
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5 tbsp. all-purpose flour
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3 c. whole milk
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1/2 c. cornstarch
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1/2 tsp. kosher salt
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1/2 tsp. baking powder
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1/4 tsp. baking soda
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1/4 tsp. cayenne pepper
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1 c. all-purpose flour, divided
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3/4 c. chilled club soda
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1 medium onion, sliced into 1/2-inch thick rings
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Vegetable oil for frying