Heat the coconut oil in a pan. Add mustard seeds, fenugreek seeds, and cumin seeds. Let them splutter.

Add chopped onions and crushed garlic. Sauté until translucent.

Add green chilies, chopped tomatoes, salt, turmeric powder, sambar powder, and garam masala. Cook until the tomatoes turn soft and mushy.

Pour in 1 cup of water and bring to a boil.

Grind pottukadalai into a fine powder using a mixer.

Add grated coconut and fennel seeds to the powder. Grind again to make a smooth paste.

Add 1/2 cup of water to the paste, grind once more, and transfer the mixture to the pan.

Add the remaining 1 cup of water, mix well, and bring the kuzhambu to a rolling boil.

Finally, add curry leaves and chopped coriander leaves. Simmer for a few minutes and turn off the heat.