To a pressure cooker, add the black chickpeas with 1 ½ cups water, season with salt and cook till ¾ ths done.
In another pan, cook the plantain along with red chilli powder, half of the turmeric powder, salt and 1 ½ cups water till done. Drain and keep aside.
Add the diced yams to the black chickpeas and cook till the yams are lightly mushy (use the back of the ladle to mash the yams if necessary). Then add the drained plantain and mix well to combine.
Coarsely crush the grated coconut, peppercorns and garlic in a mortar and pestle or grinder and add this to the cooked chickpeas. Add the remaining turmeric powder and mix well to combine.
Taste and season with salt if necessary. Cook in low heat for 1-2 minutes and remove.
To temper, heat coconut oil in a small pan and crackle the mustard seeds. Then add the curry leaves and dry red chilli. Pour this over the prepared chickpeas and mix well to combine.
Keep covered for at least 15 minutes before serving.
Enjoy with a bowl of rice and dal/lentils.