From the Sources
Avram went down to Egypt because of the famine in Eretz Yisrael. Sarai is taken away by the Egyptians and they and their houses are punished with tzaarat, leprosy.
How to eat it
Make gingerbread men and a gingerbread house. Decorate them with glace cherries to represent the boils of leprosy. Alternatively you could make 9 different gingerbread men and set them up as the four kings and the five kings.