How to Make It
Heat a grill pan. Toss the celery root with 1 tablespoon of the oil and season with salt and pepper. Grill the celery root over moderately low heat, turning occasionally, until tender and browned, 6 to 8 minutes. Transfer to a large platter, cover loosely with foil and keep warm.
Heat 1 tablespoon of the oil in a nonstick skillet. Season the fish with salt and pepper and cook over high heat just until the flesh flakes easily, about 3 minutes per side. Set the fish on the celery root, skin side up, and cover loosely with foil.
Heat the remaining 2 tablespoons of oil in a small skillet. Add the shallots and cook over high heat until golden. Add the ginger and cook just until fragrant, then add the soy sauce. Pour the sauce over the fish, scatter the cilantro on top and serve immediately.