Chicken Tetrazzini

INGREDIENTS

• 1 tablespoon unsalted butter
• Cooking spray
• 1 cup finely chopped onion
• 2/3 cup finely chopped celery
• 3/4 teaspoon freshly ground black pepper
• 1/4 teaspoon salt
• 3 (8-ounce) packages presliced mushrooms
• 1/2 cup dry sherry
• 3 ounces all-purpose flour (about 2/3 cup)
• 3 (14.5-ounce) cans fat-free, less-sodium chicken broth
• 2 1/4 cups (9 ounces) grated fresh Parmesan cheese, divided
• 1/2 cup (4 ounces) 1/3-less-fat cream cheese
• 7 cups hot cooked vermicelli (about 1 pound uncooked pasta)
• 4 cups chopped cooked chicken breast (about 1 1/2 pounds)
• 1 (1-ounce) slice white bread