Soak idli rice in enough water for 2 hrs. Then wash it thoroughly and grind it to smooth paste by adding little water. (add only 2 to 3 tablespoon of water). The batter should be thick in consistency. Heat a pan add a tablespoon of sesame oil. Save a hand full of batter and add the remaining ground rice batter to the pan and saute it until it becomes thick in consistency so that we can squeeze it using a murukku press. once done switch off the flame and remove it from the stove. Let it cool completely.
Take a hand full dough and place it in the murukku press. We need to use round holes as shown in the pic. Now heat another pan and add jaggery and 3 cups water.
Mix it until all the jaggery is dissolved completely. Now in another Kadai filter the jaggery for any impurities. Now boil the jaggery water. Once jaggery water starts to boil press the dough in the jaggery water directly. Do not overcrowd.
When it is raw it will sink in the jaggery water. Do not disturb the dough. Once it is cooked it will start to float on the jaggery water. Now remove this vermicelli on a plate. Repeat the process for entire dough. (cooking dough in jaggery water must be done batch-wise only. If you press all the dough at the same time it would be sticky and will not cook properly)
Once all the dough is prepared, transfer all the cooked vermicelli to the boiling jaggery water. Now add grated coconut, cardamom powder and give a quick mix. At this time jaggery water would be thicker in consistency. Now mix the rice batter which we reserved earlier with little water and pour it in the jaggery water and continuously mix it or else lumps would start to form.
As rice water is poured, the mixture starts to thicken and it starts to leave the sides of the pan. This is the right consistency switch off the stove. Now grease a plate or pan with ghee and pour this prepared batter in it. Let the batter cool completely. Then slice it in any desired form and serve. Jalladai Payasam is ready.