Preheat the oven to 180 C, Gas 4 and grease a 28x 18cm baking tin. Boil the dates in the water for about 5 minutes until soft, then add the bicarbonate of soda.
Cream the butter and sugar together until light and fluffy, then add the eggs and beat well. Mix in the dates, flour and vanilla essence then pour into the greased baking tin.
Cook in the preheated oven for 20-30 minutes until just firm to the touch.
Meanwhile make the sauce. Place all the ingredients in a pan over a low heat and stir together until blended, then bring to the boil. Serve ladled over the sponge along with some fresh thick cream.