Remove the stones from your dates, and chop as finely as possible.
Pour over the boiling water and leave the mixture to sit for 20 minutes or so. If you prefer no lumps, blend the mixture until smooth.
Preheat your oven to 180ºC/160ºC Fan, and get a baking dish ready - I use one that is about 1.5L in size (30x20cm ish)
Add the unsalted butter, sugar, eggs, self raising flour, cocoa powder, baking powder, bicarbonate of soda, and the black treacle into a bowl, and beat until combined - beat as little as possible so as not to over beat it.
Add in the date & water mixture, and the milk a little at a time, and mix in until smooth. It'll be a thin mixture, but roll with it!
Pour the mixture into the dish and bake in the oven for 35-40 minutes, or until a skewer comes out clean. Whilst baking, make the sauce!
For the Sauce
Add the butter, sugar, treacle, vanilla and cream ingredients to a larger pan, and heat and stir until the sugar has dissolved and the butter has melted and incorporated.
Add the dark chocolate and stir through until melted
Pour half or most of the sauce over the baked pudding
Serve with a drizzle of cream, whipped cream, or ice cream like I did and any leftover sauce!
Notes
I pour half to two thirds of the sauce onto the pudding once the pudding has been baked and I let this sauce soak in slightly when the pudding is fresh out of the oven. The rest of the sauce I pour onto each piece (with a scoop of ice cream)
There is alot of sauce so if you want less you can make half, or freeze half
This is best served fresh, but will last 3+ days in the fridge
The pudding can be made in advance and frozen
You can reheat the pudding once if you have leftovers
I use a 30x20cm size dish, but anything roughly similar works well