How to Make It
In a food processor, pulse the doenjang with the mayonnaise, ginger and lime juice. With the machine on, slowly drizzle in 6 tablespoons of the oil until well blended. Season with salt.
In a saucepan, cover the kombu with 4 cups of water and bring to a simmer; discard the kombu. Simmer gently for 5 minutes. Add the bonito and simmer gently for 5 minutes longer. Strain the dashi (broth) through a cheesecloth-lined sieve into a saucepan; discard the solids. Add the parsnips to the dashi and bring to a simmer. Cook over moderately low heat until the parsnips are almost tender, 10 minutes.
Heat a large cast-iron skillet. Add the onion wedges and cook over moderate heat, turning, until lightly charred all over, about 5 minutes. Add the onion to the dashi and simmer until tender, about 5 minutes; keep warm. Wipe out the skillet.
Heat the remaining 2 tablespoons of oil in the skillet. Season the fish with salt and pepper. Cook skin side down over moderately high heat, turning once, until cooked through and the skin is crisp, about 3 minutes per side.
Ladle the dashi and vegetables into shallow bowls and top with the fish, skin side up. Spoon the vinaigrette over, garnish with sesame seeds, radishes and cilantro and serve.
Doenjang is available at Korean markets.