Put the ginger and milk in a saucepan and bring to 70°C (160°F) then remove from the heat. Allow to infuse for 30 minutes then strain and discard the solids. Season with salt.
Just before serving, make the ginger curds two at a time in eight ramekins with a capacity of 50 ml (1¾ fl oz) each. Warm 100 ml (3½ fl oz) of the ginger-infused milk to 35°C (95°F). Mix the vegetable rennet and mineral water together. Put 2 ml (1/16 fl oz) of the rennet mixture into a syringe, swirl the milk around in the saucepan and shoot the rennet into the warm milk. Working very quickly, fill two ramekins. Repeat this process three more times until all eight ramekins are filled. Allow to set, which will take about 2 minutes.