Peel and slice the carrot and onion. Place all the ingredients for the court bouillon in a pan, bring to the boil and boil for 5 min., strain and return to the pan.
Cut the skate into convenient portions for serving and poach in the court bouillon for 10–15 min. Remove the pieces of fish carefully, drain and place on a hot dish. Heat the butter in a small, strong pan until it begins to turn brown, remove from the heat and add the vinegar very gradually to prevent spluttering. Pour over the fish, sprinkle with a little chopped parsley and serve.