In a heatproof bowl, stir together boiling water, rice vinegar, sugar, mustard seeds, and salt until the sugar dissolves. Toss the sliced scallions to coat and let them rest at room temperature for about 30 minutes.

Under cold water, rinse the jasmine rice until the water runs clear, then drain well.

In a medium saucepan, combine the rice, coconut milk, water, and salt. Bring it to a boil, then cover and reduce the heat to low. Simmer for 15-20 minutes until the liquid is absorbed, and the rice is tender. Fluff with a fork and keep warm.

Set your oven to 425°F (220°C).

Place the sea bass fillets on a sheet pan, drizzling with 1 tablespoon olive oil. Season with salt and pepper, then roast for 12-15 minutes until the fish is opaque and flakes easily. Keep warm.

In a large skillet, heat the remaining olive oil over medium-high. Add onion, garlic, Thai chili, and shiitake mushrooms. Cook, stirring occasionally, for 4-5 minutes until mushrooms soften and brown.

Stir in the miso paste until smooth, then add coconut cream, rice vinegar, and sugar. Bring to a gentle simmer and cook for 7-8 minutes, stirring often, until the sauce thickens slightly.

Add chili oil, lime zest, and lime juice. Adjust seasoning with salt and black pepper to taste; keep warm over low heat.

In another skillet, heat 1 tablespoon of oil over medium-high. Place bok choy cut-side down and cook for 7-8 minutes, turning once until lightly charred and tender. Season with salt and pepper.

Spoon coconut rice onto plates, top with roasted sea bass, and finish with a generous drizzle of the miso coconut sauce. Garnish with pickled scallions, and serve the seared bok choy alongside.