Grease the base and sides of a 20cm (8 in) square deep baking tin and line base with a square of baking parchment.
Place chopped dates in a bowl and pour over the boiling water. Add bicarbonate of soda and leave to stand.
Place all the remaining ingredients for the pudding in a mixing bowl and cream together with an electric whisk for a few minutes until light and fluffy; fold in the date mixture. Spoon into the prepared baking tin and smooth the top.
Cover with baking parchment and a double layer of foil. Scrunch edges around rim of the tin to seal.
Place pudding in a large roasting tin, and then pour boiling water into the tin until the level is halfway up the pudding.
Bake in the preheated oven for 1 hour or until a skewer inserted into the centre comes out clean.
To make the sauce, add all the ingredients to a small pan and warm gently until all the sugar has dissolved.
Serve cut into squares, drizzled with toffee sauce.