Reliquary of St. Thomas Becket, first quarter of the 12th century, Champlevé copper, engraved, chased, enameled and gilt, Musée national du Moyen Âge, Paris, Photo by Marie-Lan Nguyen via Wikimedia Common, Artwork in the Public Domain.

Just a Second: Champlevé

Champlevé

(noun)

A technique in enameling in which an artist creates hollows in a metal surface and fills it with enamel.  The artist who crafted the champlevé enamel scene on the Reliquary of St. Thomas Becket carved it into copper before filling it with enamel and covering the copper with gold.