Sprinkle baking soda over the dates. Pour over the boiling water and leave to cool. Cream the butter and the sugar in a mixing bowl, then gradually beat in the egg. Sift the dry ingredients two or three times. Fold the dry ingredients and the date mixture alternately into the butter mix using a metal spoon. Pour into a greased 25cm pie dish or cake tin. Bake at 180 Degrees C (350 Degrees F) for 45 minutes until dark brown and done (test as for a cake). Bring sugar, water and butter to the boil. Remove from heat and add vanilla and brandy. Put warm sauce over hot cake. Leave to cool. Cut tart into portions and serve with cream piped over each piece. Sprinkle with chopped nuts.