Gingery Mustard Greens and Tilapia Soup (Canh Cai Ca Ro)

  • Preparation: 25 mins
  • Cooking: 15 mins
  • Skill level: Easy
  • Servings: 4

Description Gingery Mustard Greens and Tilapia Soup (Canh Cải Cá Rô)

My Dad and I used to catch small perch at the local harbor for Gingery Mustard Greens and Tilapia Soup (Canh Cai Ca Ro). Amid the sailboats and cabin cruisers, we would lower our poles, the lines baited with thawed frozen peas, to catch the three- to four-inch-long fish, the American equivalent of Vietnamese cá rô. We would bring home about a dozen fish, and my mom would gut them for this classic Viet combination of sweet fish, sharp mustard greens, and ginger.
One day, Mom protested that cleaning the fish took too much time, so we stopped catching them, and the soup didn’t grace our table for years. On a trip to Vietnam, I saw a fishmonger at Ben Thanh market in Saigon cleaning cá rô, which reminded me of how good Gingery Mustard Greens and Tilapia Soup (Canh Cải Cá Rô) is. Back home, I decided to use whole tilapia, which is sometimes identified as cá rô in Viet markets. It worked just like traditional cá rô in Vietnamese cooking, but its larger size made it much easier to prep and cook. Now, this brightly flavored Vietnamese soup is back on my table as an ideal balance for bold, rich foods like Vietnamese-Style Grilled Lemongrass Pork Riblets. Whole tilapia is sold at Asian and Latin markets.


  • 7½ cups water
  • 1 tilapia, 1 to 1¼ pounds, cleaned and cut into 3 sections (head and 2 body sections)
  • 1 yellow onion, thinly sliced
  • ¾ teaspoon salt
  • 1½ tablespoons fish sauce
  • 1 tablespoon canola or other neutral oil
  • ⅛ teaspoon black pepper, plus extra for garnish
  • ½ pound mustard greens, stems removed and leaves cut into bite-sized pieces (4 packed cups)
  • 1½ tablespoons peeled and minced fresh ginger

Method Gingery Mustard Greens and Tilapia Soup (Canh Cải Cá Rô)

1, In a 3- or 4-quart saucepan, combine the water, fish, half of the sliced onion, and ½ teaspoon of the salt and bring almost to a boil over medium-high heat. Lower the heat to a simmer and use a ladle to skim and discard any scum that rises to the top. Let simmer for 10 minutes, or until the flesh of the fish is opaque. Transfer the body sections to a plate, but leave the head in the broth. Let the broth simmer for another 10 minutes.
2, Meanwhile, let the body sections cool for a few minutes, then remove the meat and discard the skin and bones. A fork and a soupspoon are handy for this task. It is okay if the flesh does not come off in large pieces.
3, When the broth has finished simmering, remove from the heat and pour through a fine-mesh sieve into a clean saucepan. Discard the solids. Add 1 tablespoon of the fish sauce and cover and set aside if not serving right away.
4, In a skillet, heat the oil over medium heat. Add the remaining onion and cook gently, stirring occasionally, for about 4 minutes, or until fragrant and soft. Add the fish and heat for about 1 minute, or until heated through, gently breaking it up into 1-inch pieces as it heats. Add the remaining ¼ teaspoon salt and 1½ teaspoons fish sauce and the ⅛ teaspoon pepper and cook for 1 to 2 minutes to allow the fish to absorb the flavors. If you are not serving the soup right away, turn off the heat and cover.
5, Just before serving, return the broth to a simmer. Add the mustard greens and cook for about 1 minute, or until they have wilted and turned deep green. Add the ginger and the fish and stir gently to distribute the fish evenly. Taste and add extra salt or fish sauce, if necessary. When the soup is at a simmer, turn off the heat and ladle into a serving bowl. Sprinkle with black pepper and serve immediately.

Chef's Note

The soups, as well as many other Vietnamese Soup Recipes, include gently cooking onions until they are fragrant and soft. This unhurried step is called phi hành and takes about four minutes to complete over medium heat.
The purpose is to coax the sugars from the onions without browning them. You know the onions are ready when you stick your nose over the pan and the harshness of onion has been transformed into a sweet aroma. The onions will have lost their opacity and turned translucent, and they will have lost all their crispness and become limp. Note that phi hành shouldn’t be confused with the crispy fried shallots called hành phi.
There are two schools of canh making: the drop-into-boiling-water school and the sauté-first-then-simmer school. Cooks who follow the former practice argue that their method produces a pristine, clear broth. I prefer to extract extra flavor from some of the ingredients, such as onion, by sautéing them first and then adding the seasonings and water. A brief simmer follows and the soup is done.
The broth is not quite as clear as with the drop-into-boiling water method, but the flavors are stronger.

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