INGREDIENTS
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4 boneless, skinless chicken breasts (about 2 pounds total), pounded to 1/2-inch thick
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1 tablespoon olive oil
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3 tablespoons unsalted butter
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10 ounces cremini mushrooms, thinly sliced
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1/2 medium yellow onion, diced
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1/2 teaspoon kosher salt, plus more for seasoning
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1/4 teaspoon freshly ground black pepper, plus more for seasoning
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4 cloves garlic, minced
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2 tablespoons all-purpose flour
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1 cup half-and-half or whole milk
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1/2 cup low-sodium chicken broth
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1/2 cup finely grated Parmesan cheese (about 1 ounce), plus more for serving
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2 tablespoons chopped fresh parsley leaves