Score the skin of the fish using a sharp knife then season all over. Heat a little olive oil in a non-stick frying pan. Fry the fish skin side down for three minutes (put a small plate on top to keep the skin in contact with the pan).
Carefully turn the fish and continue to cook for a further minute, then remove from the pan and rest while you finish the dish. Add the peas and veg stock to the pan, cover and cook for two minutes.
Add the lettuce and dill plus a small knob of of butter and mix.
Season with sea salt and lemon juice. Season the fish flesh side with lemon juice and the skin side with sea salt then serve with the peas and lettuce.