Chicken Tetrazzini

This is a fabulous recipe I got from my friend Dorene. We make it regularly. Enjoy!
Chicken Tetrazzini
1 C. Diced Celery
1 C. Diced Green pepper
1 C. Diced onion
1 C. Sliced mushrooms
2 t. salt
1/4 t. pepper
3 C. Cooked, cubed chicken
1 lb. Cooked spaghetti
1/2 c. butter
1/4 c. flour
1 c. Milk
1/2 lb. grated sharp cheddar
1 garlic clove, crushed
2 T. Worcestershire
1/4. c. Sherry
3/4 c. shredded Parmesan

Boil water and cook spaghetti. Meanwhile; Cook veggies and mushrooms in butter until onion is transparent. Add flour and blend. Add milk stirring constantly. Add cheddar, salt, pepper, garlic, Worcestershire, chicken and Sherry. When cheese is melted, mix with spaghetti. Place in casserole and top with Parmesan. Bake at 350 for 20-30 minutes.