The recipe I found (along with my deviations) was:
- 35 cl brandy
35 cl water
200 g sugar (I used 150 g muscavado sugar)
60 g root ginger
1 vanilla pod (I used 1/2 tsp vanilla paste)
Zest of an orange
Peel and thinly slice the ginger. Bring the water, ginger, vanilla (split if using pod) and sugar to the boil, then lower the heat and simmer for 20 minutes or until the ginger is tender. Allow to cool and add to a sealable jar. Allow the syrup to cool. Add the orange zest and the brandy. Seel the jar and give it a shake. Allow to steep for two or three days (remove the vanilla pod after the first day if you want to limit the vanilla taste). Strain and bottle.
It's very drinkable after a day or two, with a pronounced orange nose from the zest and a heat in the mouth from the ginger. Using the dark muscavado sugar I expect this to mellow over a considerable period of time.
With the syrup dilution the end result is a little bit under 20%, so quite a mild liqueur.