Soak the urad dal overnight. Grind to a thick coarse batter with just a generous splash of water. Allow to rest for at least an hour.
Soak the rice for 2 odd hours. Wash and grind to a thick coarse batter. Again, just a splash of water. Allow to rest for an odd hour or so.
Mix the dal and rice batters thoroughly, leave overnight to ferment.
Mix the grated coconut, jaggery and cardamom powder in a pan, cook over a low flame, stirring occasionally. Till the jaggery is well incorporated into the coconut. 5-7 odd minutes I would reckon. Remove from heat.
Add a sprinkle of salt and black pepper to the batter, give it a hearty mix.
Heat water in a steamer.
Take a turmeric leaf, trim the top and bottom ends, grease lightly with oil.
Place a spoonful of batter with a spoon in the middle of the turmeric leaf, spread it evenly. Top it with a spoonful of the jaggery-coconut filling as shown in the picture.
Gently fold the turmeric leaf lengthwise, so that the filling is now covered by the batter from the top as well as the bottom.
Tie with a twine, steam for 8-10 minutes.
Allow to cool down, gently remove the turmeric leaves and serve.