Combine water and dates, boil 3 minutes or until thick. Remove from stove and add marshmallows, salt and vanilla. Stir until smooth; cool slightly. (Add walnuts, optional). In flat pan, 9 x 9 x 2 inches) crush Oreo cookies, spread evenly on the bottom of pan. Pour cooled filling evenly over cookies (well crushed).
Whip cream, add sugar to taste and spread on top of ingredients already in pan. Finish by crushing 3 or 4 more Oreo cookies and sprinkling on top of whipped cream. Chill at least 1 hour before serving.
