Skin and bone the eel, cut in 2 to 3 inch lengths, and put in a saucepan with enough cold water to cover, add the sliced onions, turnip, and the chopped herbs. Season with salt and peppercorns. Bring to the boil and simmer for 15 to 20 minutes till the eel is tender. Place the cooked pieces of eel on a hot dish and pour over them a sauce made with the butter, with which the flour has been mixed, and a few tablespoons of eel stock added gradually. Add finally 1 tablespoon of chopped dill. Serve with cucumber salad. The cucumber should have been peeled and sliced, freely sprinkled with salt, and left to stand for 2 hours, so as to extract the water.