Soak tamarind in 1 cup of hot water and extract its pulp.

Keep tamarind pulp aside.

Heat 1 tablespoon of oil in a heavy-bottomed pan.

Add mustard seeds to the hot oil.

Wait for the mustard seeds to crackle.

Add cinnamon stick and curry leaves to the pan.

Sauté for about 1 minute.

Add chopped onion and sauté until soft and translucent.

Add diced brinjal and potato to the pan.

Mix well to combine.

Cover the pan and cook until the potatoes and brinjals are half cooked (3-4 minutes).

Add finely chopped tomato and cook until mushy.

Add tamarind pulp, turmeric powder, red chilli powder, and salt.

Let it cook for 3-4 minutes.

In a mixer jar, combine grated coconut, khus khus, fennel seeds, cashews, and dry red chillies.

Grind to a smooth paste.

Add the paste to the gravy.

Boil for 2-3 minutes.

Turn off the heat and serve hot.

Serve Kathiri Urulai Masala Kuzhambu with South Indian breakfast items like Idli, Dosa, Kerala Parotta, or for dinner with Rotis or Steamed Rice and Beetroot Raita.