Stuffed Chicken Breasts | America's Test Kitchen

Ingredients

• 4 boneless, skinless chicken breasts (8 ounces each) (see note)
• 3 tablespoons vegetable oil
• 10 ounces white mushrooms , trimmed, wiped clean, and sliced thin
• 1 small leek , white part halved lengthwise, washed, and chopped (about 1 cup)
• 2 medium garlic cloves , minced or pressed through garlic press (about 2 teaspoons)
• 1/2 teaspoon chopped fresh thyme leaves
• 1 tablespoon juice from 1 lemon
• 1/2 cup dry white wine
• 1 tablespoon chopped fresh parsley leaves
• Salt and ground black pepper
• 1 cup low-sodium chicken broth
• 1 teaspoon Dijon mustard
• 2 tablespoons unsalted butter