Preparation of nage: Bring all ingredients to a strong boil in a very large saucepan. Turn down the heat so that the liquid is just barely simmering. Hold there for three and a half hours. Remove the skillet from the heat and allow the liquid to cool.
At the end of the cooking time, there should still be the one and a half liters of nage remaining in the saucepan to make the dish. Now strain the liquid through a fine-mesh kitchen sieve and then reserve.
Preparation of the dish: cut the scallops horizontally about four millimeters thick tranches # from a scallop thus give three slices.
Lightly butter fireproof soup plates and pour in the scallop slices in a single layer. Season lightly (!) with salt and pepper. Heat the oven to maximum (280 to 300 °C ).
Spread a few flakes of butter evenly over the mussel slices and place the plates in the oven ten centimeters apart from the top heat. Leave there # with the oven door open # for at least a minute. When the meat is slightly set, remove the plates on the spot and baste the mussel layer with the hot nage. Sprinkle plenty of chives on top and bring to the table with plenty of bread # crusty or freshly toasted.
(*) The nage: “[…] Monsieur Jean now applied a so-called nage. This is what the Minchellis called their clear soups, which they ever made with fish of any kind and many herbs.