Skin the sole, remove the heads and blood clots behind the heads and rinse well. Trim off the fins and the ends of the tails with a pair of scissors. Butter an ovenproof pan or dish large enough to take the fish without overlapping, put in the fish and add the fish stock and
Meanwhile, moisten the breadcrumbs in the remaining sherry, then melt
When the liquor is syrupy, pour in the cream and bring back to the boil. Reduce the heat to low and gradually add the remaining butter in small pieces, beating with a small whisk until it has all melted (once you have added the butter do not let it come back to the boil).