You can use any firm fish here. There are a few unusual ingredients here, like the fenugreek and the tamarind. Fenugreek will be in most spice sections of larger supermarkets. It adds a lot and I recommend you look for it at least, although you can leave it out.
2to 5 chiles,such as Thai, Tabasco, arbol or serrano
4clovesgarlic,chopped
1 1/2inchpiece of tamarind,or 1 tablespoon tamarind paste
1/2cupwater(coconut water is nice here)
1can of coconut milk
TO FINISH
2tablespoonsvegetable oil or clarified butter(ghee)
1onion,sliced
2to 5 jalapenos,sliced
1/3cupchopped cilantro
Instructions
Toss the chunks of fish in the lemon and salt and set aside as you chop the vegetables.
Put everything from the curry mix except the coconut milk into a food processor or blender and puree. If it's too chunky and gunks up your machine, add enough of the coconut milk to let the motor run smoothly. Set it aside.
In a deep-sided pan, heat the vegetable oil or clarified butter over medium-high heat. Cook the onions until they are soft, and a little browned on the edges, about 6 minutes. Add the sliced jalapenos and the fish and toss to combine. Pour over the curry mix and the rest of the coconut milk. It should be a thick gravy. If it's too thick, add a little water or some more coconut milk if you have some. Let this simmer for 10 minutes, then add the cilantro. Let this cook for 1 minute, then serve with rice.