First peel the ginger and cut it into very fine strips. Mash the cinnamon stick and cardamom pods and cut open the vanilla stick.
Put 2/3 of the ginger, cinnamon, cardamom as well as the vanilla, the rock sugar and the sea salt in a saucepan, add water and bring to the boil. Let the brew cool down completely.
Strain after cooling, pour the collected stock into a well-sealable glass vessel, add the remaining ginger and rosemary sprig and top up everything with the schnapps.
Let the mixture stand in a dark place for about 8 weeks, shaking occasionally.