Cheesy Chicken Tetrazzini

Wow. It has been over a week since I have put up any recipes. So sorry about that. This baby in my belly makes me tired so when I get a few minutes to myself I usually want to rest. Not that sitting at the computer is such hard work but you know what I mean. This dish was good. I found a recipe but didn't have everything it called for so I started making stuff up. Here is what I came up with

3 boneless skinless chicken breast cooked
1 (7 ounce) package spaghetti (just how ever much you want really)
1/4 cup of butter or margarine
1 medium onion chopped
2 1/2 TBS flour
1 cup milk
1 can cream of mushroom soup
1/4 tsp garlic powder
1/4 cup chicken broth (I just use what I have cooked the chicken in, close enough)
1 (4 ounce) can sliced mushrooms drained
1/2 cup Parmesan cheese
8 slices of American cheese
1 cup cheddar
Cook spaghetti. In a saucepan saute onion in butter until tender. add flour and stir well. Reduce heat and stir in next ingredients thru the American cheese. Cook slowly until cheese is melted and sauce is smooth. Cut chicken into bite-sized pieces. Add to sauce and stir. Remove from heat. Drain spaghetti and combine with sauce mixture. Season with salt and pepper. Stir well. Spray a 9 X 13 dish with nonstick cooking spray. Pour in casserole. Top with cheddar cheese. Bake at 350 for 20 to 30 minutes.