Puff Pastry Chicken Potpie

Ingredients (15)

• 1 package (17.3 ounces) frozen puff pastry, thawed
• 2 pounds boneless skinless chicken breasts, cut into 1-inch pieces
• 1 teaspoon salt, divided
• 1 teaspoon pepper, divided
• 4 tablespoons butter, divided
• 1 large onion, chopped
• 2 garlic cloves, minced
• 1 teaspoon minced fresh thyme or 1/4 teaspoon dried thyme
• 1 teaspoon minced fresh sage or 1/4 teaspoon rubbed sage
• 1/2 cup all-purpose flour
• 1-1/2 cups chicken broth
• 1 cup plus 1 tablespoon half-and-half cream, divided
• 2 cups frozen mixed vegetables (about 10 ounces)
• 1 tablespoon lemon juice
• 1 large egg yolk