Grease a 1.2 litre/2 pint pudding basin with butter. I use the plastic lidded bowls that are made for steamed puddings but you can use a more traditional pudding bowl if you are able to cover and tie it closed at the top. (see tips in content above)
Beat the butter and sugar together until pale and thickened a little. This takes a few minutes.
Add the eggs and milk and mix again for a couple of minutes.
Add the flour and cocoa and beat thoroughly.
The batter should be a soft dropping consistency. Add a splash more milk if it's not.
Empty your batter into your pudding bowl with a spatula.
Place the lid on your pot and secure. Place your pot in the slow cooker and fill around it with just boiled water from the kettle so that it comes three quarters of the way up the side of your pudding bowl.
Cook on high for three hours. You can also steam this pudding in a saucepan too for 2 hrs and 30 minutes.
Whilst the pudding is cooking just before you want to serve it melt the chocolate, milk and cream gently together in a saucepan. Pour into a jug for easy pouring.
When your pudding is cooked carefully remove from the bowl and invert onto your serving plate.
Cut into wedges and serve with lots of chocolate sauce.
Notes
Grease your pudding bowl generously.
Use a plastic lidded pudding bowl for ease.
Add an extra splash or two of milk if needed to make sure the batter is a soft dropping consistency.
Reheat leftovers covered in the microwave
You can steam this pudding in a saucepan too for 2 hrs and 30 minutes.