"... he presents her with sugar-plums ... which he puts into her mouth playfully."

Sugar plums, associated with the Victorian Christmas, were made of fruit (not  necessarily plums). The dried fruit was finely chopped and combined with chopped almonds, honey and aromatic spices.This mixture was then rolled into balls, and coated in sugar or shredded coconut.

A video recipe of how to make Victorian sugar plums can be found at http://www.bbc.co.uk/victorianchristmas/activity/sugar-plums.shtml.