Shrimp paste is made by salting tiny shrimp or krill, letting them ferment and then grinding or sun-drying the mash. Thai kapi is a soft, grayish-purple paste; Malaysian and Indonesian belacan and terasi come as firm, dark blocks that are toasted before use; Vietnamese mắm tôm is a wetter, mauve paste eaten as a dipping sauce. The smell is aggressive raw, but cooked into a Thai curry paste, nam prik kapi, fried rice or Malaysian sambal belacan it turns into a deep, rounded savoriness nothing else provides.

How to buy

Buy the type your recipe names. For Thai dishes look for a plastic tub of kapi (Pantai, Tra Chang or Nang Fah brands); for Malaysian sambal buy a block of belacan (Cap Tiga Udang); for Vietnamese bún đậu buy a jar of mắm tôm. The ingredients should be shrimp and salt only, with a pinkish-gray to purple color rather than bright red dye. Asian grocers and Amazon stock all three; a 3–7 oz container lasts a year because you use so little.

How to store

Kept sealed in the fridge, shrimp paste lasts well over a year; the salt is the preservative. Double-bag or jar it to stop the smell spreading. It may darken and firm up, which is normal. Discard it only if you see mold or it smells ammonia-sharp rather than fishy-salty. Blocks of belacan can also be frozen in slices.

Substitutes

  • Anchovy paste, 1:1 – closest in salt and funk, a little fishier and smoother.
  • Fish sauce, 2 tsp per 1 tsp paste – supplies the salty umami without the thick, fermented depth.
  • Miso plus a dash of fish sauce, 1:1 – vegetarian-friendly if you skip the fish sauce, but milder and sweeter.
  • Dried shrimp, ground, 1 tbsp per 1 tsp paste – shrimp flavor without the fermented punch; add extra salt.

How to use

A teaspoon flavors a curry for four; measure carefully, because it is roughly as salty as soy sauce and impossible to remove. Always cook it: fry it in oil with the aromatics, or wrap a block in foil and toast it in a dry pan until fragrant, then crumble it in. Balance it with lime juice, sugar and chiles, and do not add extra salt or fish sauce until you have tasted the finished dish.

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