Step 1: The Overnight Infusion (Do the day before)

Mix the Tiger's Milk: Whisk together the 50g lime juice, 20g lemon juice, mirin, sesame oil, and salt in a bowl. Stir in the minced lemongrass, minced ginger, sliced shallot, and half a lime leaf. Cover tightly and refrigerate overnight.

The Pickling Liquid: In a small saucepan, combine the white wine vinegar, white wine, water, cane sugar, salt, sliced ginger, galangal, lemongrass, and lime leaves. Bring to a boil, then immediately turn off the heat and let the aromatics steep until completely cool.

Pickle the Shallots: Place your razor-thin shallot rings into a small glass jar. Bring the cooled pickling liquid back to a boil, then strain it directly over the shallots through a fine sieve. Seal the jar and let it cool to room temperature before storing it in the fridge.

Step 2: The Morning Prep (3 to 4 hours before serving)

Butcher the Black Cod: Carefully slide a long, sharp knife between the flesh and the skin of the black cod. Cut the white flesh into clean, even 8mm cubes. Place them in a bowl, cover, and keep chilled in the fridge. Scrape off any dark flesh left on the skin. Stretch the skin completely flat and taut over a silicone baking mat. Dry it in a dehydrator or an oven at 50°C (122°F) for 3 to 4 hours until completely brittle.

Make the Cornstarch Fluid Gel: Blanch the lime peels in boiling water 3 separate times (using fresh water each time) to remove bitterness. Blend the blanched peels, 60g lime juice, salt, sugar, ginger syrup, water, and deseeded jalapeño until glass-smooth. Pour the liquid into a saucepan, reserving 1 tablespoon of cold liquid in a small bowl. Whisk the 5g of cornstarch into that reserved tablespoon to form a smooth slurry. Bring the saucepan to a bare simmer over medium-low heat, whisk in the slurry, and bring to a gentle boil, stirring constantly for 60 to 90 seconds until thick and clear. Pour into a shallow container, press plastic wrap directly onto the surface, and chill for 1 to 2 hours until cold and set like a pudding. Scoop the cold starch block into a clean blender and process on high for 30 seconds until it shears into a glossy, silky fluid gel. Transfer to a piping bottle and refrigerate.

Bake the Onion Taco Shells: Slice the 2 onions thin and glaze them slowly in a pan with a splash of oil over the lowest possible heat until completely soft and translucent. While they cook, take the reserved dry onion peels and char them with a kitchen blowtorch until black and smoky. Dry them at 50°C for an hour, then grind into a fine powder. Weigh out 67g of your soft, glazed onions and blend them with the egg white, sunflower oil, sugar, and salt until smooth. Fold in the flour. Divide the batter into two bowls. Mix a teaspoon of your charred onion powder into one half to turn it dark. Spread the dark batter thinly onto a taco-mesh stencil mold and bake at 160°C (320°F) for 8 minutes. Remove, spread a thin layer of the light, neutral batter over it, and bake for another 10 to 12 minutes until crisp. While still hot from the oven, punch out clean circles with a round cutter and quickly drape them over a taco stand or rolling pin to mold them into curved shells.

Step 3: Service Prep (1 hour before serving)

Puff the Skin: Heat a small pot of frying oil to 200°C (392°F). Using tweezers to hold the dry fish skin flat, drop it into the oil for 2 to 3 seconds until it instantly puffs up. Drain on paper towels and immediately dust with fine salt and cayenne pepper. Snap into shards.

The Avocado Cream: Scoop the meat from your ripe avocado into a blender with the juice of ¼ lime and 2g of salt. Process on high speed until completely glassy and velvety. Transfer to a piping bag and chill.

Strain the Tiger's Milk: Pour your overnight ceviche marinade through a fine sieve into a clean bowl, using the back of a ladle to press out every drop of flavor. Discard the spent aromatics.

Step 4: Assembly & Final Plating

Cure the Fish: Pour the strained cold Tiger's Milk over your diced black cod 35 to 40 minutes before serving. The high fat content of the sablefish needs this extra time to firm up and turn beautifully opaque. Once cured, drain the liquid away thoroughly.

Assemble the Tacos: Lay your crisp onion taco shells in a serving holder. Pipe a continuous, thin line of the cold lime and jalapeño fluid gel along the very bottom of each shell. Carefully spoon the drained, buttery black cod ceviche into the shells. Top the fish with a tiny pinch of flaky sea salt. Pipe elegant, alternating dots of the vibrant green avocado cream and extra jalapeño fluid gel over the fish. Gently arrange 3 or 4 pickled shallot rings along the top, nestle a few crispy shards of the puffed cayenne fish skin into the cream, and scatter white leek flowers and tiny coriander leaves across the surface. Serve immediately!