* Round Steak should be cut 3/4 to 1-inch thick. ~- Cut round steak into serving size pieces. Combine dry mustard, salt and pepper; sprinkle over round steak and pound on both sides with meat mallet. Brown steak quickly in oil in large frying pan. Pour off drippings. Drain liquid from mushrooms and add enough water to make 1/2 cup. Add liquid and Worcestershire sauce to steak. Cover tightly and cook slowly for 1 1/2 hours. Add mushrooms during last 5 minutes of cooking time. Remove steak to warm serving platter and top with mushrooms. Garnish with carrot curls and parsley or celery leaves.