For the Fire Glaze, begin by smoking the fish bones. Line the base of a large saucepan or wok (not non-stick) with foil and place over high heat. Spread woodchips over the base of the pan and ignite with a blowtorch or match until chips just begin to smoke. Line a bamboo steamer with baking paper and piece several holes in the paper. Place the steamer into the saucepan or wok, place fish bones into steamer and cover with steamer lid. Cover the pan with a lid or layers of aluminium foil, reduce heat to low and allow bones to smoke for 15 minutes.
Once smoked, transfer bones to a small saucepan, place on the stove top over medium heat and add the pisco. Once the pisco is simmering, reduce the heat and continue to simmer over low heat until reduced by half. Strain through a fine sieve, discard bones and set aside until needed.
Meanwhile, place gochujang, sugar, diced kaiserfleisch and 200ml water into a medium saucepan, place over medium heat and bring to a simmer. Once simmering, add the reduced pisco and butter and simmer for 10 minutes, or until reduced to a thick glaze. Strain the glaze through a fine sieve. Reserve the diced kaiserfleisch, keeping warm until needed for serving. Set aside the glaze, keeping warm until needed.
For the Grated Kohlrabi, peel the kohlrabi and grate using a wasabi grater. Place grated kohlrabi in a small bowl and set aside in the fridge until needed.
For the Pickled Kohlrabi, use a mandolin to slice the kohlrabi into very think slices, about 1mm thick.
Place the pisco and white vinegar into a medium bowl and stir to combine. Place the kohlrabi slices in the pickling liquid and toss well to coat. Set aside in fridge to pickle for 10 minutes. When pickled, remove the kohlrabi from the pickling liquid, pat dry and set aside in the fridge until needed.
For the Flame Grilled Cobia, trim cobia fillets into thick, 6cm square portions.
Place the flour and salt and pepper to taste in a medium bowl and mix to combine. Place the cobia fillets in the bowl and dust in seasoned flour.
Place a large frypan on the stovetop over a medium heat and add the oil. Shake excess flour off the cobia fillets and add to the pan. Fry cobia portions, skin side down, for 4 minutes then turn and fry for a further 2 minutes. Remove pan from heat and set aside.
Place a wire rack over an open flame on the stovetop. Brush cobia portions generously with the Fire Glaze and place onto rack, skin side down. Cook the fillets, glazing often, until cooked through and charred, about 3 minutes. Remove fish from rack and set aside to rest until ready to serve. Keep the wire rack over the flame for the Grilled Kaiserfleisch.
For the Grilled Kaiserfleisch, brush the sliced kaiserfleisch generously with the Fire Glaze and place on to the wire rack over the open flame. Grill until crisp and golden. Remove from wire rack and set aside, keeping warm until needed.
To serve, place a fillet of Flame Grilled Cobia onto each serving plate. Add a spoonful of Grated Kohlrabi and some Pickled Kohlrabi slices to one side of the fish. Add a spoonful of the diced kaiserfleisch next to the Grated Kohlrabi. Place a slice of Grilled Kaiserfleisch next to the Pickled Kohlrabi. Garnish with a few mushroom leaves and small kohlrabi leaves. Serve with extra Fire Glaze on the side.