Made of cast iron with enamel coating and designed by Patricia Urquiola. Cast iron is one of the metals with the most suitable thermal properties for this type of crockery and for the related cooking. 
Cast iron does not exchange heat quickly, and therefore does not drop in temperature when you place steaks onto it. Upon contact with the piping hot pan surface, the meat is seared, sealing in all its juices. This makes for excellent rare steaks, but well done ones too without making them dry.