In Hansel and Gretel, what is the house of the witch made of?

Hansel and Gretel are siblings who are abandoned in a forest and fall into the hands of a witch who lives in a gingerbread, cake, and candy house. The witch, who has cannibalistic intentions, intends to fatten Hansel before eventually eating him. However, Gretel saves her brother by pushing the witch into her own oven, killing her, and escaping with the witch's treasure. Set in medieval Germany, "Hansel and Gretel" has been adapted into various media, including the opera Hänsel und Gretel by Engelbert Humperdinck, which was first performed in 1893.

Source: Wikipedia