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Salted Crab – Boo Kem (or Bpoo Kem)

Kasma Loha-unchit, April 30th, 2009

Salted crabs (Boo Kem) are an ingredient foreign to many westerners.

Salted Crab

Salted Crab, 3-1/2 inches wide

In my childhood days, I was fascinated by the myriad moving, darting and crawling creatures inhabiting the edge of the pond that wrapped around two sides of my family’s property. Among them were these small black crabs, no larger than a small Louisiana crayfish; they scurry through the rushes and sometimes venture across the wide expanse of our lawn to the sedges at the edge of our neighbor’s pond. Their strange sideways movement always caught my curiosity, but whenever I approached one, it would come to a complete halt, raising its front pincers up toward me, its alarmed eyes protruding out from their sockets and moving side to side to study me closely. I had even come across ones that would foam around their mouths. A bit too ominous for a small child to touch!
Salted Crab Green Papaya Salad

Salted Crab in Green Papaya Salad

(Click on an image to see a larger version.)

These small freshwater crabs are found in great numbers in and around ricefields and flatlands turned into wetlands during the rainy season. Though they do not have much meat, they are caught and fermented in salt water, making a briny crab sauce for seasoning. They are then called boo kem (or boo kem), salted crab. The best part, though, are the crabs themselves, which are cut up into chunks shell and all, and added to salads, including the delicious Salted Crab Green Papaya Salad (Som Tam Boo Kem) – to this day my favorite rendition of this popular national dish. They are also cooked in saucy dishes to lend their flavor, and make a wonderful sauce with chopped pork, shrimp and coconut cream for serving with crisp vegetables, aromatic herbs and rice (see recipe,  below).

Since other Southeast Asian cultures also delight in the flavor of salted crabs, these small black crustaceans can occasionally be found among the unusual offerings of ethnic markets located near areas where large concentrations of Southeast Asians have settled. Look for them in small plastic pouches or containers in a refrigeration unit.

Crab Coconut Cream Sauce (Loen Boo Kem) Recipe

One Brand of Salted Crab

One Brand of Salted Crab



  • 6 small salted crabs
  • 2 cups coconut cream
  • 1/4 lb. ground pork
  • 1/4 lb. fresh shrimp, shelled and chopped finely
  • 1/4 cup tamarind juice the thickness of fruit concentrate
  • 1/4 cup palm or coconut sugar
  • Sea salt as needed to taste
  • 2 small shallots, quartered lengthwise and sliced thinly crosswise
  • 1 red or orange serrano pepper, cut into fine slivers with seeds
  • 1 green serrano pepper, cut into fine slivers with seeds
  • 4 red and green Thai chillies (prik kee noo), cut into 2 segments
  • Assortment of fresh firm and crisp vegetables, such as green or long beans, snap peas, cauliflower and cucumber; and sprigs of leafy aromatic herbs, such as mint and basil
Salted Crab Dip

Salted Crab Dip

Pull off the back shell of the salted crabs and discard. Remove the gills and cut each crab into four pieces, each piece with a few legs attached to a body part. Rinse and drain.

Heat the coconut cream in a saucepan over medium heat until smooth. Spoon out 2 tablespoons and reserve for later use. Add the ground pork and chopped shrimp, stirring to break into small bits as they cook. When most the pork has lost its raw pink color, add the crab pieces and return to a boil. Season sauce to taste with palm sugar and tamarind.

Simmer uncovered for ten to fifteen minutes. Taste, and if it is not salty or sweet enough, add a little salt and palm sugar. Stir in the sliced shallots and slivered red and green serrano peppers. Return to a boil, stir and transfer to a sauce dish. Let cool for ten to fifteen minutes. Top with the reserved coconut cream and garnish with the Thai chillies.

Vegetable Platter for Salted Crab Dip

Vegetable Platter for Salted Crab Dip

Arrange the vegetables on a platter and serve with the salted crab coconut sauce. The sauce may also be eaten with plain steamed rice. Suck on the crab pieces for a burst of salty crab flavor.

Serves 8-10 in a multi-course Thai meal.

Notes and Pointers:

Dip the vegetables and herbs into the sauce to eat, or place a few pieces at a time on the side of your dinner plate and spoon a little sauce over them. Dip and nibble-eat as you desire, rather than serve it as a course. The sauce may also be spooned a small amount at a time onto a little bit of rice and eaten to clear the palate after spicy bites from other dishes in the meal.

In addition to mint and basil, many other kinds of leafy aromatic herbs and strong-tasting vegetables found in Southeast Asian markets are delicious with this sauce, such as polygonum (called “rau ram” by the Vietnamese), sawleaf coriander (oblong leaves with serrated edges), rice paddy herb (rows of very small green leaves growing up soft, light green stems), lemon mint and edible chrysanthemum leaves. Bitter and astringent vegetables like bitter melon (warty, oblong squash) and fresh banana blossom also make good accompaniments, as the sauce softens their strong bite. Look for these unusual produce in Asian markets near you and give them a try, or substitute with strong-tasting salad greens, such as arugula, radicchio, endive, sorrel and parsley.

Banana Blossom

Banana Blossom

If you wish to try out the exotic banana blossom, it is available from time to time during the warmer months in Southeast Asian markets. The outer layers are a rich purplish red color, but the best parts for eating are the light ivory leaves in the center. Because the sap can blacken the heart and leaves, soak in salted water immediately after cutting. Banana blossom has an unpleasant astringent bite (an acquired taste) when eaten by itself, but this disappears when accompanied by the creamy sauce – a very unusual experience!

Note: This originally appeared in Kasma’s second cookbook, Dancing Shrimp: Favorite Thai Recipes for Seafood (now out of print).

Kasma’s website includes information on many Thai ingredients.

Written by Kasma Loha-unchit, April 2009.

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