Rinse and soak the chickpeas in water overnight or for at least 6-8 hours.
Drain the soaked chickpeas, rinse once again and add them to a pressure cooker with fresh water. Cook on high for 8-10 whistles or until soft but not mushy.
Once the pressure releases, take about 3-4 tbsp of boiled chickpeas in a mixie jar and grind to a smooth paste. Keep aside.
Meanwhile, heat oil in a kadai over medium heat. Add sliced onion, chopped ginger, garlic, dry red chillies, curry leaves, coriander seeds and grated coconut. Roast all the ingredients on medium flame till they release flavour and turn a golden brown, about 5 minutes. Then cool and grind to paste along with turmeric powder and garam masala powder. Keep aside.
Heat oil in the same pan and add chopped tomato. Cook until the tomatoes soften. Then add the ground chickpeas paste and the ground masala paste. Sprinkle salt and sauté for about 5 minutes.
Then add the boiled chickpeas and ½ cup of the cooking liquid. Simmer for 10 minutes, allowing the flavours to meld. Once you get the desired consistency, turn off the gas.
Now in a small pan, heat a little coconut oil. Sizzle curry leaves, dry red chilli and mustard seeds. Add the sliced onion and fry for 1-2 minutes.
Pour this tadka over the kadala kari.
Serve Kerala Kadala Kari with steamed rice or appam.