In a large saucepan, melt butter over low heat. Stir in the package of dressing mix. Blend in chicken broth and cream of chicken soup. Mix in cream cheese and sour cream, and stir until smooth. Heat through, but do not boil. Arrange chicken breasts in a single layer in a 9x13 inch baking dish. Pour sauce over.
Bake until done in the preheated oven.
Twenty minutes before the chicken is done, bring a large pot of lightly salted water to a rolling boil. Cook pasta until al dente, about 5 minutes. Drain. Serve chicken and sauce over pasta.