To prepare the bottom layer, sprinkle soda over chopped dates; then pour boiling water over the dates and let stand until cool. Cream sugar, butter and egg, and beat well. Add flour, baking powder and chopped nuts to creamed mixture and mix well. Add this to the date mixture and mix well. Bake in a greased 9 X 9 pan for 30 minutes at 350 degrees F.
To prepare the topping, combine sugar, water, chopped dates and chopped nuts in a sauce pan. Bring to a boil, stirring constantly; boil until mixture thickens. Spread over cooled bottom layer. Let cool. Serve with Cool Whip on top.