Clean the anchovies thoroughly and set them aside.
Soak a little tamarind in a few tablespoons of water and keep it aside.
In a mixer or a food processor, add the grated coconut, small onions, green chillies, turmeric powder, cumin, fennel, garlic, ginger, curry leaves and salt.
Pulse them into a coarse paste and set it aside.
Heat coconut oil in a pan over medium heat.
Add mustard seeds and let them splutter.
Add curry leaves and sauté for a few seconds.
Add the cleaned anchovies and salt to the pan and sauté for a few minutes until they start to cook.
Add 3 teaspoons of tamarind water, cover and cook for 5 minutes stirring occasionally.
Add the coconut mixture to the pan.
Mix everything well and cook on low heat for about 10 minutes, stirring occasionally, until the anchovies are cooked through and the flavours meld together.
Check the seasoning and add more salt if needed.
Remove from heat and let it rest for a few minutes.
Serve hot with steamed rice or as a side dish with other Kerala-style dishes.