Melt 2 tablespoons of butter or margarine in a large saucepan over medium heat. Add 1 cup chopped onion, 1 cup chopped carrots, and 1/2 cup chopped celery. Saute for about 10 minutes, until the onions and celery are clear, and the carrots are soft. Add the chunked chicken, and season with salt and pepper to taste. Transfer the chicken/vegetable mixture to a medium to large pot. Add 2 cans of chicken broth, and 1 1/2 cups of uncooked noodles. Place over medium heat, and bring to a boil. Reduce heat to low, cover pot with a lid, and simmer about 15 minutes, until the noodles are cooked through and all the flavors are blended. Ladle soup into individual serving bowls. Serve with saltine crackers. Guaranteed to make you feel better, if you are feeling under the weather!