Soak rice submerge in water for at least 3 hours. Drain the liquid and in a wet grinder grind the rice for 5 minutes. now add the coconut and grind for another 5 minutes coarsely. NOTE: grind the dough soft not too hard. like you do for medium vadai.
Now pick the dough about he size of big goose berry. Make a ball and flatten it. place a piece of Jaggery in middle and cove and make a ball. do the same with the rest of dough.
In a pan or pressure cooker add water as needed (i.e. until the balls can submerge) and bring to boil.
Now add the balls (urundai). let it stay there for 5 minutes. note if you stir the balls will dissolve. after 5 minutes you are good to stir gently. cook this for 15 more minutes or until cooked by gently stirring few times.