Preheat your oven to 180°C (160°C fan) or Gas Mark 4. Grease four individual pudding moulds or ramekins with butter.
Place the chopped dates and bicarbonate of soda into a bowl. Pour over the boiling water, stir, and set aside to soak while you prepare the rest of the ingredients.
In a mixing bowl, cream together the butter and caster sugar until light and fluffy. Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract.
Gently fold in the flour, followed by the milk, until you have a smooth batter. Finally, stir in the date mixture, including any remaining liquid.
Divide the batter evenly between the prepared moulds or ramekins, and place them on a baking tray.
Bake in the preheated oven for 20-25 minutes, or until the puddings are well-risen and firm to the touch. A skewer inserted into the centre should come out clean.
While the puddings are baking, prepare the toffee sauce. Combine the muscovado sugar, butter, cream, and black treacle in a saucepan over medium heat. Stir until the sugar has dissolved and the sauce is smooth and bubbling gently.
Once the puddings are ready, remove them from the oven and let them cool for a minute. Run a knife around the edges to loosen, and then turn them out onto serving plates.
Pour the warm toffee sauce generously over each pudding and serve immediately. Enjoy your sticky toffee puddings with a dollop of cream or a scoop of vanilla ice cream if desired.