Skin the monkfish very thoroughly, removing all gristle and gelatinous skin. Cut from the central bone, leaving two thick fillets. Cut each into 4 equal slices.
Gently heat the butter in a frying pan. Peel the rhubarb, and cut into slender batons about
Add the fish stock to the frying pan, which will also contain some cooking juices from the monkfish. Reduce by half over a high heat. Season to taste. Strain on to heated dinner plates, and arrange the monkfish and rhubarb on top. Garnish liberally with the greenery, which is also important for the overall flavour of the dish.