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