Wash the Nashi pears, remove the core and coarsely grate them together with the ginger. Add lemon juice to prevent the pears from turning brown. Add the preserving sugar to the rasps and let the juice steep for about 30 minutes. Then let it boil until the pear rasps are soft - that took me about 10 minutes.Make a gelling test and add a packet of citric acid if necessary. Fill into twist-off glasses while still hot, close tightly and turn upside down for about 15 minutes. I used mini nashi pears from our garden, so I didn`t peel them. The Nashis from the supermarket are much larger, and you can safely peel them.