This heady combination of seafood and tomato comes from the north, where it is traditionally made from small rice-field crabs called cua đong. To extract enough flavor, cooks use many crabs, removing their back shells and pounding their bodies. The crushed crab is combined with water, carefully filtered, and finally mixed with fermented shrimp sauce (mam tom) to create a broth base. When heated, the crab solids rise to the top, forming a rich, seafood-laden floater that is the signature of the soup. Sections of the floater are carefully spooned atop round rice noodles (bun) before the broth is ladled into each bowl. A garnish plate of raw vegetables, limes, and fresh herbs accompanies the soup. When I was a child, our family re-created this soup by using the tiny rock crabs foraged among the rocks at the local harbor. Nowadays, I make this more convenient and equally tasty version. Unlike many Vietnamese Americans (including my mom), I don’t use canned bún riêu cua soup base. Rather, I start with a live Dungeness crab and mix its meat and tomalley with ground shrimp and egg for the floater. Since Dungeness crab season (November through May) doesn’t coincide with tomato season, I use premium canned tomatoes instead of fresh ones. If you are substituting other types of crab, you will need enough to yield 6 ounces of meat.

　　

Ingredients

serves 6

　　

Broth

3 1/2 quarts (14 cups) plus 1 1/4 cups water

　　1 live Dungeness crab, 1 1/2 pounds

　　2/3 cup dried shrimp

　　1 3/4 teaspoons salt

　　2 tablespoons fish sauce

　　8 egg whites, lightly beaten

　　3 tablespoons canola or other neutral oil

　　1 yellow onion, finely chopped

　　1 can (28 ounces) whole tomatoes, coarsely chopped with juices reserved

　　3 tablespoons fine shrimp sauce

　　

Bowls

1 pound small dried round rice noodles, cooked in boiling water for 3 to 5 minutes, drained, and flushed with cold water

　　2 or 3 scallions, green part only, thinly sliced

　　1/4 cup chopped fresh cilantro, leafy tops only

　　

Garnishes

1/4 to 1/3 pound water spinach stems, split into fine shreds, soaked in water to curl, and drained, or leaves from 1 small head romaine lettuce, halved lengthwise and cut crosswise into 1/4-inch-wide ribbons

　　3 cups bean sprouts (about 1/2 pound)

　　3/4 cup thinly sliced banana blossom bract (leaf), soaked in acidulated water, massaged with warm water, and drained well (optional; see Note)

　　2 or 3 limes, cut into wedges

　　12 to 20 sprigs Vietnamese balm and/or Thai basil (optional)

　　Spoonful of fine shrimp sauce (optional)

　　Mellow Chile-Garlic Mix (page 315), optional

　　

Step 1

Pour the 3 1/2 quarts water into a 5- or 6-quart Dutch oven and bring to a rolling boil over high heat. Add the crab and cook, clean, and pick it as directed on page 322. Set the meat and the tomalley and fat aside. If you don’t like the tomalley and fat, discard them along with the shell bits. Reserve 3 quarts (12 cups) of the cooking liquid for the broth.

　　

Step 2

To rehydrate the dried shrimp, put them in a small saucepan with the 1 1/4 cups water, bring to a simmer over medium heat, and cook for 10 minutes, or until slightly soft. Drain the shrimp into a sieve placed over a bowl and let cool completely. Add the cooking liquid to the reserved crab cooking liquid.

　　

Step 3

Put the cooled shrimp in a food processor and process to grind to a coarse texture. Add the crabmeat and tomalley and fat. Pulse 3 times to combine but not pulverize the crabmeat. Transfer to a bowl and mix in 1/2 teaspoon of the salt, 1 tablespoon of the fish sauce, and the egg whites. Set aside.

　　

Step 4

In a large, wide pot, heat the oil over medium-high heat. Add the onion and cook, stirring occasionally, for about 3 minutes, or until fragrant and a bit soft. Add the tomatoes and their juices and the remaining 1 1/4 teaspoons salt and bring to a vigorous simmer. Cook, stirring frequently, for 10 to 12 minutes, or until most of the liquid has evaporated and the mixture is thick.

　　

Step 5

Add the shrimp sauce, the remaining 1 tablespoon fish sauce, and the reserved cooking liquid. Bring to a boil over high heat, lower the heat to a gentle simmer, and cook for 30 minutes.

　　

Step 6

Meanwhile, bring a large pot of water to a rolling boil, for reheating the noodles; ready the scallions and cilantro for assembling the bowls; and arrange the garnishes on a plate or put them in small dishes and put on the table.

　　

Step 7

Keeping the broth at a gentle simmer, use a large spoon to slowly stir it in one direction, scraping the bottom of the pot. As you stir with one hand, use the other to pour in the egg mixture. Keep stirring, and as soon as the egg mixture floats to the top, remove the spoon. Let the broth cook undisturbed for 5 minutes. When small bubbles break the surface, the soup is done. The broth underneath will be golden and clear with some solids at the bottom. Lower the heat so the broth stays warm while you assemble the bowls.

　　

Step 8

When the water has reached a boil, place a portion of the noodles on a vertical-handle strainer (or mesh sieve) and dunk the noodles in the boiling water. After 5 to 10 seconds, pull the strainer from the water, letting the water drain back into the pot. Empty the noodles into a bowl and repeat with the remaining portions, while proceeding to assemble each bowl.

　　

Step 9

Use a slotted spoon to transfer an equal portion of the floater to each bowl, on top of the noodles. Bring the broth to a rolling boil, taste, and salt, if necessary. Ladle 2 cups broth into each bowl, distributing the hot liquid evenly. Top with the scallions and cilantro. Serve immediately with the garnishes. It is customary for diners to add some vegetables, torn herb leaves, and squeezes of fresh line. Anyone wanting a brinier bowl should mix in a dab of shrimp sauce, while heat seekers should add a little of the chile-garlic mix.

　　

Notes

Step 10

To split and curl water spinach stems, use only the hollow portion of the stems, removing all leaves and tender stems (save those for a stir-fry, page 178). Soak the stems in water for 5 minutes to make them easier to split. A knife is traditionally used to split the stems, but a water spinach splitter (dao che rau muong, literally “knife for splitting water spinach”), available at Vietnamese markets, works much better. The thin metal rod attached to the round plastic top contains a set of sharp blades arranged like wheel spokes. Slide the splitter into the stem and then push the stem through the blades until about 4 inches of split stem protrudes. Grab the split portion and pull on it to drag the remaining stem portion through the blades. Deposit the shreds in a bowl of cold water and let soak for 15 minutes to curl. Drain before using.

　　

Step 11

For information on banana blossoms, see page 52. Simply remove some of the bracts, stack them, and then slice them. Soak for 10 minutes in 1 tablespoon of distilled white vinegar and water to cover. Then massage and drain them.

　　Reprinted with permission from Into the Vietnamese Kitchen: Treasured Foodways, Modern Flavors by Andrea Nguyen. Published by Ten Speed Press, an imprint of Penguin Random House. Copyright © 2006.  Photographs by Leigh Beisch. Buy the full book from Amazon or Bookshop.