Grease a 1.2 litre pudding basin and line the base with a circle of baking paper. 

Cut out and grease a 35cm square piece of foil.

Into a small bowl mix half the gin, the golden syrup, the tonic syrup (if using it) and 1 tbsp of the ginger syrup.

Once mixed, put it, and the slices of stem ginger into the bottom of the pudding basin.

In a food processor (you can mix this by hand, but this is far easier and quicker) put all the other ingredients and mix until combined. 

Spoon the batter into the basin and level it as much as possible (don't worry too much, it'll even out in the cooking).

Take the foil and laying it flat, fold 2 pleats in the centre. Put to on top of the basin, greased side down and secure with string around the rim of the basin. Finally, before cutting the string, take it up over the top to create a loose handle (this saves burning your fingers later), then tie off securely.

Pop the pudding on an upturned saucer in a suitably large saucepan and fill with enough boiling water to come two-thirds up the side of the basin. Pop the lid on the pan, turn on the heat, and bring it up to a simmer. Cook on this gentle simmer for two hours. Check on the water level every 30 minutes and top it up with more boiling water, as to use cold will bring the temperature down and will make it sink. 

Finally, when done, turn off the heat, and remove the basin from the pan. Cut the string, remove the foil and using a spatula, loosen the pudding around the edge of the basin. 

Turn out onto a place, remove the greaseproof paper, and serve warm with custard or ice cream