How to Make It
In a large, deep flameproof roasting pan, combine the chicken stock, wine and dissolved fish bouillon cubes. Arrange the celery in the pan with all the ribs facing the same direction. Arrange the scallions perpendicular to the celery. Scatter the ginger and reserved lemon ends over the vegetables. Cover the pan with foil, set it over 2 burners and bring the liquid to a boil.
Arrange the oysters on the floating vegetable mat. Cover the pan with foil and simmer until the oysters just begin to open, 3 to 5 minutes. Using tongs, carefully transfer the oysters to a platter. With a knife tip or a small spoon, open the oysters and tip some of their juices into the broth. Serve the oysters warm or at room temperature.
Continue to simmer the broth until it is reduced by half, 35 to 40 minutes. Strain the broth into a medium saucepan, then ladle it into small bowls or rimmed soup plates. Garnish with the lemon slices and a pinch each of the chopped parsley, cilantro, ginger and shallots; serve piping hot.