How to Make It
In a blender, combine the soy sauce, red wine vinegar, pickled ginger and brine, miso paste, sherry vinegar and chopped radish and puree until smooth. With the blender on, drizzle in the 1/4 cup of olive oil. Season the vinaigrette with salt and pepper and transfer to a small bowl.
Light a grill and oil the grate. Season the snapper cavities with salt and pepper and fill with the poblano, thyme sprigs and lemon slices. Tie the fish with kitchen string at 2-inch intervals. Generously brush the fish with olive oil and season lightly with salt and pepper.
Set the fish on the grill, cover and grill over moderate heat, turning once with large spatulas, until the flesh just flakes with a fork, about 20 minutes. Carefully transfer the fish to a platter. Remove the kitchen strings. Using 2 forks, lift the fillets off the bones and transfer to plates.
In a medium bowl, toss the sliced radishes with the sprouts and 2 tablespoons of the vinaigrette. Top the fish fillets with the radishes. Drizzle a little of the remaining vinaigrette around the fish and serve.
The vinaigrette can be refrigerated overnight.