Pain d’épices (m.) is French for “gingerbread.” Notice that the actual word for “ginger” is nowhere to be found in pain d’épices. The word literally means “bread of spices.” You can use the word on its own as a noun, or as a flavor.
Here’s an example:
Les enfants vont construire une maison en pain d’épices.
(The children are going to build a gingerbread house.)
Again, its descriptive form can be accomplished by adding a preposition—in this case, with en preceding the whole word. Notice the lack of the accent aigu (acute accent) on the second “e” in épices, which points to the word meaning “spices” as opposed to “spiced.”