Put the dates in a heatproof bowl, pour over the boiling water and stir in the bicarbonate of soda. Leave to soak for 10 minutes.
Grease and line a 20 cm (8 inch) square cake tin.
Beat together the butter, sugar, eggs, flour, baking powder and soaked dates and their frothy liquid in a bowl. Pour into the prepared tin. Place in a preheated oven, 180°C (350°F), Gas Mark 4, for 25–30 minutes until firm to the touch.
Place all the sauce ingredients in a saucepan while the pudding cooking, and heat through until the sugar has dissolved. Cut the sponge into 8 pieces and serve warm in bowls topped with some thick cream, the toffee sauce and a scattering of pecan nuts.