Wash and soak Urad dal for 4-5 hrs. Place in a big vessel as it will expand after soaking.
Then drain water from the Urad dal and grind to fine paste adding very little water.
In fact just about a teaspoon of water should be enough. The batter is almost like the thick dosa batter before you make dosas. Add salt and leave it aside covered.
I had to in fact use more than 1 tsp to bring it to the said Dosa like batter consistency. I think I used about 3-4 tsps. Use your discretion to add water.
For the filling, pressure cook the channa dal with just enough water to cover it. Even if excess water is there, you can always use the water for chaaru. But less water is better.
Cook the jaggary to remove any scum. Then once the dal is well cooked, drain and cook it along with the jaggary. It should become very soft enough for you to mash well. You can either grind it to a smooth paste or mash it with the lentil masher. If you find the purnam is very loose, you can cook this in sim to get a thick paste.
Add Cardamom powder and grated coconut. You will know its done when the dal starts to leave the sides.
Once I cooked the dal, I mashed it lightly immediately.
Then in a skillet, I added the grated jaggery in low heat.
Then I added the lightly mashed lentil to it.
Then once it started to thicken a bit, added the coconut and cardamom to it.
Divide them into equal balls.
Heat a thick bottom kadai for frying. Once the oil is hot, turn to sim. Then dip each ball in the Urad dal batter.
ensure its coated on all sides.
Then gently drop them into the hot oil.
Turn and cook on all sides. Since the filling is dal based, it tends to steep into the oil. That's why you will see dark spots on the sweets. Once couple of batches are done, strain the oil to remove the scum.
It hardly takes more than 2-3 mins to get cooked. Drain them on to a kitchen towel.
Since the batter used is of Urad dal, we can also make savory doughnut or the Medhu Vada. Add onions and other spices and deep fry them as regular vadas.