Soak chickpeas in water overnight or for 6 hours.
Apply tamarind paste and salt to yam and soak in water for 2 hours. This removes the itchiness of the yam.
Boil chickpeas, yam and ½ cup onion by pressure cooking them. Switch off the gas after 5-6 whistles and wait for the pressure to get released naturally. Drain and keep it aside. Retain the water.
Heat a kadai and add oil. After oil gets heated, add remaining chopped onion and saute.
After onion turns pinkish, add peppercorns, cloves, coriander seeds and dry red chilies and mix well.
Add grated coconut and roast till coconut turns brownish. Aroma of roasted coconut should fill the air.
Switch off the gas or heat. Add turmeric powder and marble sized ball of tamarind and stir.
Let this roasted coconut masala cool down.
After cooling down, grind it by adding 1 cup water (preferably the water in which yam and chickpeas were boiled) and keep aside. This makes the gravy.
Switch on the gas and in the kadai, add boiled chickpeas and yam.
Over this pour the ground gravy from the mixer.
Let it simmer for 15 minutes. If gravy thickens, add some water.
Adjust salt to taste.
Garnish with chopped coriander leaves.