Pat pork tenderloin dry. Combine mustard, thyme, salt and pepper. Rub into pork. Heat oil in a roasting pan or skillet that can be used on direct heat and in the oven. Brown meat on all sides. Add wine to the pan and roast in preheated 350F/180C oven 45-50 minutes or until a meat thermometer registers 160F/70C.
Remove meat from pan and reserve. Add cream to juices remaining in pan and scrape up any bits of meat stuck to the bottom of the pan into the sauce. Bring sauce to a boil and simmer gently until slightly thickened. Adjust seasoning if necessary.
Meanwhile, slice pork and return it to the sauce. Heat gently before serving. Sprinkle with parsley.