MIX TAMARIND CONCENTRATE, IF USING, WITH 2 TABLESPOON HOT WATER (IF USING LIME JUICE INSTEAD, ADD JUST BEFORE SERVING). PUT TAMARIND, ONION, GINGER, CORIANDER, MINCED CHILLIES, TURMERIC, CAYENNE, 1 TEASPOON SALT AND THE COCONUT MILK IN A BLENDER AND WHIRL UNTIL VERY SMOOTH.

POUR COCONUT MILK MIXTURE AND 1 CUP WATER INTO WIDE, DEEP POT AND BRING TO A SIMMER. ADD POTATOES, HALVED CHILLIES, AND CARROTS; COVER AND SIMMER, STIRRING OCCASIONALLY, UNTIL TENDER, ABOUT 20 MINUTES.

ADD FISH, SPINACH AND CURRY LEAVES AND SIMMER UNTIL FISH CHUNKS ARE OPAQUE ALL THE WAY THROUGH, ABOUT 5 MINUTES. STIR IN PEAS, SIMMER 1 MINUTE AND SEASON WITH SALT ( I USED FISH SAUCE ) TO TASTE AND LIME JUICE IF USING.