In a shallow dish, combine the flour, salt, paprika and pepper. Add beef strips; turn (or toss) until well coated. , In a large skillet, melt butter. Brown beef in batches. Remove and keep warm. Add onion and garlic to the pan; cook until tender. Add the broth, mustard, chili sauce and mushrooms; return beef to the skillet. Cover and cook until the meat is tender, about 1 hour., Just before serving, stir in sour cream. Heat through, but do not boil. Serve over noodles. Garnish with parsley.