Poach chicken in a large pot of simmering water. Cook until no longer pink in center, about 12 minutes. Remove from pot and set aside. Bring chicken cooking water to a boil and cook pasta in it. Drain. Cut chicken into small pieces, and mix with noodles.
In a separate bowl, mix together mushroom soup, chicken soup, and sour cream. Season with salt and pepper. Gently stir together cream soup mixture with the chicken mixture. Place in a 2 quart baking dish.
Melt butter in a small saucepan, and remove from heat. Stir in crumbled crackers. Top casserole with the buttery crackers.
Bake at 350*F. for about 30 minutes, until heated through and browned on top.
My Note: I couldn't help but tweak it a little since there was such great opportunity for flavor enhancement. Sometime I added a couple of cloves of garlic, 2 stalks of finely diced celery, and 1/2 of a small onion, also finely diced. I also added about 1/2 teaspoons of thyme, and about 1/2 bag of frozen mixed vegetables. I increased the cooking time to about 45-50 minutes, so that the added vegetables would get cooked. The last thing I changed was I added about 3/4 can of milk to the soup mixture to give it a little moisture so it wouldn't dry out.
Update: I sprinkled the chicken w/kosher salt & fresh ground pepper and spinach & herb seasoning that I get from Tastefully Simple -- but you could use any herbs you like. Then I browned it over fairly high heat in butter and olive oil, removed the chicken and set aside. Added about 1/2 cup chicken broth to the pan and scraped up all those yummy bits, then added the chicken back to the pan and covered & cooked till done. Remove chicken and reduce broth by half (1/4 cup). I cooked the noodles in water and the remaining chicken broth from the can, drained & added the cut chicken to the noodles. Mixed cr. of chicken w/ herbs soup & mush soup w/ sour cream & added the reduction. Mixed that w/ a little more herb seasoning. Added chicken & noodles & combined well. Topped w/ shredded cheddar and cracker crumb mixture. WOW! My son ate 3/4 of the casserole and my grandchildren LOVED it! A definite add to the rotation!