For the pudding, preheat the oven to 200C/400F/Gas 6. Butter the pudding basins really well with a third of the softened butter, then dust with the plain flour.
Place the dates and the water in a saucepan and bring to the boil.
Whisk the remaining butter and the sugar together in a large bowl using an electric beater until light and fluffy. Gradually add the golden syrup, treacle, vanilla extract and eggs to the mixture and continue beating. Turn the beaters down to a slow speed and add the self-raising flour, a spoon at a time. Beat until all the ingredients are well combined.
Purée the hot water and date mixture in a food processor or blender and add the bicarbonate of soda. Quickly add this to the mixture in the bowl while it is still hot. Stir to combine and fill two or three 7.5cm/3in metal pudding basins (or one 12.5cm/5in pudding basin) with the mixture.
Bake in the oven for 20-25 minutes until the top is just firm to the touch.
For the sauce, place all the sauce ingredients into a pan and bring to the boil. Remove from the heat.
To serve, remove the puddings from the moulds and put on a serving plate with lots of the hot sauce on the top. Serve with ice cream.