Pressure cook the green gram with water for 6-7 whistles (or 3 whistles depending on the cooker). If it has been soaked overnight, 1 or 2 whistles would do.
Grind together the grated coconut and cumin seeds together to make a smooth paste.
In a deep bottomed vessel, add the cooked green gram. To it, add the turmeric, red chilli powder, salt and the green chilli (slit). Boil the green gram for a couple of minutes.
Add the coconut and cumin paste and boil the mixture until the coconut paste is cooked. Set this aside.
In a pan, heat oil and add the mustard seeds, red chilli and curry leaves and let them splutter. Add this seasoning to the green gram mixture.
Serve hot with rice or roti.