Cheesy Chicken Tetrazzini

1 cup water
¼ tsp salt
1/8 tsp pepper
4 boneless chicken breast halves
6 cups water
½ tsp salt
1 T oil
1 (7-oz) package spaghetti
1 medium-size green pepper, chopped
¼ cup butter, melted
2 ½ T flour
1 ¼ cups milk
1 (10 ¾ oz) can cream of mushroom soup, undiluted
1 (4-oz) can sliced mushrooms, drained
1 (2-oz) jar diced pimiento
1/8 tsp garlic powder
½ cup grated Parmesan cheese
3 cups shredded Cheddar, cheese, divided

    Combine first 3 ingredients in a saucepan; bring to a boil.  Cut chicken into ½-inch cubes.  Add chicken; cover, reduce heat, and simmer 10 minutes or until done.   Drain chicken.
    Combine 6 cups water and next 2 ingredients in a Dutch oven; bring to a boil.  Add spaghetti, and cook 10 minutes or until almost tender.  Drain well, and set aside.
    Saute green pepper in butter in a Dutch oven until tender.  Add flour, and stir well.  Stir in milk, next 5 ingredients and 2 cups cheese.  Cook over medium heat, stirring constantly, 10 minutes or until thoroughly heated.  Stir in chicken. 
    Spread half of spaghetti in a greased 13 x 9 inch baking dish; spread half of chicken mixture evenly over spaghetti.  Repeat layers.  Bake at 350° for 15 minutes.  Sprinkle with remaining 1 cup cheese; bake an additional 5 minutes.  Yield:  6-8 servings.