These mirror-like plates are actually porcelain. Poured and hand finished to produce the reflective sheen, this setting is called Miroir de Sorciere, and indeed it recalls the "scrying mirrors" used as a divination tool by magical practitioners.
Above is an impressive display in her eponymous shop. What blows me away is that most of these settings are in a matte finish!
Her store is located at 37 Rue de Beaune, Paris... if you find yourself in the area, stop in and ogle these art works for the table.