Thanks for asking. It's a crumb of some type. I was too agog at the prospect of my nice meal that I forgot to note down all the details from the menu. Can assure you that it was delicious. The crumb added a nice texture to the soft scallop and the butter's smoothness and flavouring didn't overpower things.
Good point. I nicked the description from an indicative menu on their website as I forgot to note what it said on the menu when I went there. Clearly they altered it since then. Will edit title of point post. I definitely did eat it!