Lightly brown chicken in butter in a skillet; remove and set aside. Saute onion in pan drippings until tender; blend in flour, salt, paprika, and pepper. Cook over low heat until bubbly. Gradually add chicken broth; cook, stirring constantly, until smooth and thickened.
Remove from heat, stir in sour cream and worcestershire sauce.
Cook noodles according to package instructions, drain. Combine noodles and half of sour cream sauce. Spoon into a shallow 2 litre casserole. Top with chicken, pour remaining sauce over chicken. Bake at 160ºC or 1 hour.