The idea for this rich soup comes from a method popular in northern France and in Belgium for cooking eels in a broth that is finished with cream and thickened with egg yolks. The cream can be kept to a minimum and the egg yolks can be left out entirely. It is the abundance of fresh herbs, chopped and added at the last minute, that makes this soup a revelation.
– leeks, white part only, cleaned and thinly sliced.
– 2 tablespoons butter.
– 4 pounds whole fish such as red snapper, sea bass, and/or red mullet cleaned, filleted, fillets skinned, heads and bones reserved, and fillets cut into 1-inch cubes.
– Bouquet garni.
– 5 cups hard cider.
– ½ to 1 cup heavy cream.
– 6 egg yolks (optional).
– 1 bunch parsley, preferably flat-leaf, large stems removed and leaves finely chopped at the last minute.
– 1 tablespoon finely chopped fresh tarragon, chopped at the last minute.
– 1 tablespoon finely chopped fresh mint, chopped at the last minute.
– 1 tablespoon finely chopped fresh chives, chopped at the last minute.
– 1 bunch sorrel, stemmed (optional) and finely chopped at the last minute.
Step 1:In a pot, cook the leeks in the butter over low to medium heat, stirring regularly, for about 10 minutes, or until they soften but do not brown. Add the fish bones and heads, bouquet garni, and cider and simmer gently for 30 minutes. Remove from the heat and work the mixture through a large-meshstrainer or a food mill fitted with the coarse disk into a clean pot. If using the egg yolks, don’t use an aluminum pot, or the egg yolks will turn gray.
Step 2:Stir the cream to taste into the strained broth. If using the egg yolks, in a bowl, whisk them for 1 minute, or until they are slightly pale, and then whisk in about one-third of the broth. Pour this mixture back into the rest of the broth, and put the pot over medium heat. Stir with a wooden spoon for about 3 minutes, or until the soup is silky and smooth and the tiny ripples turn into smooth waves. Don’t let it boil.
Step 3:Stir in all the herbs and the fish and season with salt and pepper. Reduce the heat to low—again, don’t let the mixture boil—and stir for about 3 minutes, or until the fish is cooked and the flavor of the herbs is infused.