We are not 100% sure this is a pot de creme cup, only because at 4.5" tall and the narrow base it could have been made for another purpose. The cup was produced by the Longwy factory in France. The decoration is a distinctive pattern decorated in the style of Henri II. The handle is a stylized gargoyle. The colors are interesting in shades of burgandy/rust with teal accents.
Longwy Workshop is a ceramics company located in Longwy, France that dates back to 1798. The company still exists today and produces products under the brand Societe des Fainceries de Longwy et Senelle. The company produced ceramics many of which were glazed to look like enamel metal similar to cloisonne. They also produced many serving pieces including pot de creme cups.