1

Season the pieces of ling with some salt. Bring the chicken stock to a boil in a small pan and keep hot.

2

Melt half the butter in a wide, shallow casserole that can be used for serving. Add the onions, and cook gently for 2 to 3 minutes, until tender but not browned. Add the quartered lettuce hearts and turn them over once or twice in the butter. Add the peas, hot chicken stock, and some salt and pepper, and simmer rapidly for 3 to 4 minutes, turning the lettuce hearts now and then, until the vegetables have started to soften and about three-fourths of the liquid has evaporated. Put the pieces of ling on top of the vegetables, then cover and simmer for 7 to 8 minutes, until the fish is cooked.

3

Shortly before the fish is done, heat a ridged cast-iron grill pan over a high heat. Pan-grill the pancetta or bacon for about 1 minute on each side, until crisp and golden. Keep warm.

4

Uncover the casserole, dot the remaining butter around the pan, and sprinkle the chopped chervil or parsley over the vegetables. Shake the pan over the heat until the butter has melted and amalgamated with the cooking juices to make a sauce. Garnish the fish with the pan-grilled pancetta, take the casserole to the table, and serve with some small new potatoes.