Heat the oven to 180 ºC. Chop the dates, quite coarsely, using a heavy knife, and place them in a bowl. Sprinkle the bicarbonate of soda over the dates and pour over the boiling water. Set aside to cool slightly.
Put the butter and sugar into a large bowl and, using an electric whisk, cream together until pale, light and fluffy. Break the egg and gradually incorporate it into the butter/sugar mixture. Beat for another minute.
Sift the flour, salt and baking powder into the mixture. Add the warm date/water mixture and very gently fold everything together.
Pour the mixture into a deep 22 cm buttered ceramic or glass pie dish. Bake at 180 ºC for 30-40 minutes, or until the cake is well risen, dark brown and cooked right through.

Syrup:  Put the water and brown sugar in a saucepan and bring gently to the boil, stirring frequently to dissolve the sugar crystals. When the syrup is clear, remove from the heat and stir in the brandy and butter.
Remove the cake from the oven. Pour the hot syrup, in batches, over the hot cake, tipping the dish so that it sinks in evenly.  The syrup will bubble furiously at the edges of the dish.

Serve it warm with whipped cream.