Preheat the oven to 180ºC (160ºC fan). Line a 20 cm square tin with non-stick baking parchment.
Put the dates in a bowl with the hot water and bicarbonate of soda. Leave to soak.
In another bowl cream the butter and sugar together until pale and creamy. Add the eggs one at a time, mixing well after each one. Add the date mixture and mix well, then fold into the flour.
Pour the mixture into the prepared tin and bake for 25-30 mins or until springy to the touch and a skewer comes out clean.
To make the sauce combine the sugar and butter in a small saucepan with half the cream. Gently bring to the boil over a medium heat and stir until the sugar has dissolved. Add in the treacle and let the mixture gently simmer for 1-2 mins until well co0mbined. Remove from the heat, and add in the remaining cream.
To serve cut the warm pudding into portions, pour the toffee sauce over and serve.