Cromesquis = as far as I could see online and in a Dictionary of Gastronomic terms I have - are deep fried croquettes - small "balls" of say, foie gras - at best, or snails mixed with butter, mixed with herbs some flour and an egg.

Florence's answer makes sense in the sense that beurre de ....could mean a location or what the beurre is made of. For sure beurre de croquettes would seem strange - but unless Florence knows ZEE village in Normandy that is called Cromesquis and is sure it exists, I am a bit skeptical about the Normand connection.

Could it be cromesquis de foie gras placed on or around the entrecôte?