• Prep

• Peel shallot and cut into thin slices.
• Slice lemongrass and pound it gently with the side of a knife.
• Peel garlic and ginger and mince.
• Rinse serrano and cut into thin slices. Scrape out the seeds if you want a less spicy soup.
• Rinse the tomatoes and coarsely chop.

In a medium pot, warm 2 tablespoons oil over medium heat until hot but not smoking. Sauté shallots and lemongrass with a pinch of salt until soft, 2 to 4 minutes. Add garlic, ginger and serrano, and stir until fragrant, about 30 seconds. Toss in the tomatoes, increase the heat to high and let cook, 2 to 4 minutes. Add the fish bones and 3 cups water. Bring to a boil, reduce to a simmer and let cook without stirring until flavors have infused, about 15 minutes.

• Meanwhile:

• Slice fish on a sharp angle and toss with fish sauce.
• Rinse the bok choy and slice crosswise into ½-inch pieces.
• Rinse and dry cilantro and coarsely chop.
• Cut lime into wedges.

Remove the fish bones and lemongrass from broth and discard. Add the sliced fish and bok choy and cook until fish is opaque and flakey and the bok choy is tender, about 4 minutes.

Remove from the heat. Season the soup to taste with salt and add a squeeze of lime. Divide between two bowls, garnish with cilantro, fried garlic, sesame oil and serve with the remaining lime.