A New Zealand tradition. Mrs. Boyes was the grumpy head cook at the Rosemount Inn when I worked there as a dishwasher twenty-some years ago. She was all right but you did not want to get on her bad side. I managed to avoid that in the two months that I was there and she was really, a very good cook.
I have made this for years using regular sugar. I omit the ground rice and increase the flour by about 1/2 C., or to desired texture and firmness of dough. It is probably not the authentic cookie, but it is a good substitute.