Cut a large square of baking parchment and another of tin foil. Make a pleat in the centre of each square. The pleat gives the pudding room to rise. (If you have a pudding basin with a lid you can skip this step.)
Place an upturned saucer in the bottom of a large saucepan with a lid and put the kettle on.
Grease a 1.2 -1.5 litre pudding basin well. Scatter the chopped ginger in the base and drizzle over the golden syrup.
Mix together the flour, baking powder, ginger, cinnamon, mixed spice and salt in a large bowl. Add the cold butter and rub it in using your fingertips until the mixture resembles fine breadcrumbs and no lumps of butter remain.
Stir in the sugar then add the treacle and milk and stir until well combined.
Pour the batter into the prepared pudding basin and spread it level.
Place the baking parchment on top of the pudding basin with the pleat in the middle, followed by the tin foil. Press the foil over the edge of the pudding basin.
Tie a length of string very tightly several times around the foil – there should be a lip on the pudding basin; tie the string just under that.
Tie a length of string across the top of the basin to make a handle. Trim off the excess foil and parchment, leaving at least a centimetre below the string. If your pudding basin has it’s own lid, skip the above and simply put the lid on, making sure it is tight.
Place the pudding basin on top of the saucer in the pan. Pour boiling water into the pan so that it comes about halfway up the pudding basin. Do not let the water touch the foil/baking parchment otherwise you may end up with a soggy pudding.
Put the lid on the pan and place over a low heat. Cook at a gentle simmer for 2 hours, it will do the pudding no harm to let it cook for a while longer however. Check halfway through to see if the water needs topping up but resist the urge to take the lid off the pan too often.
When it is cooked, the pudding should be springy to the touch and a skewer inserted into the centre should come out clean.
Remove the tin foil and parchment. Run a knife around the edge of the pudding to loosen it then place a serving platter on top and flip it over. The pudding should drop out of the basin (you might need to give it a bit of a shake).
Serve straight away with custard or ice cream.