Soak urad dal with sufficient amount of water for around 2 hours .Drain the water from the soaked dal and transfer it into a grinder / mixer . Add little drained water kept aside and grind urad dal to a smooth paste . Add drained water in steps and continue grinding urad dal until it froths up and increases in quantity.

Wash the idli rava and drain out all the water; Add rava to the urad batter and grind for another 3-4 mins until it blends well with the batter .

Transfer the ground batter to a big vessel , add salt , mix well and keep aside for fermentation . let it ferment for 10-12 hours .

In the morning , you will see that idli batter would have raised and fermented well . Kadubu batter is ready .

Pick semi tender big jackfruit leaves . If its too dry , the leaves will break while folding and pricking .Hence pick only semi tender ones . Wash it nicely , wipe it and keep aside .

Take 4 equal jackfruit leaves.Hold and pin 2 leaves together with the help of the coconut leaf sticks as shown in pic .

Place another 2 leaves on the pinned leaves such that all the tips are facing each other (ref pic )

Pin all the leaves together .

Now bend 2 leaves upwards , fold them in "L" shape and pin them together along the edges till the tip of the leaves .

Similarly take the 3rd leaf , fold and pin together along the edges till the tip of the leaves .

Repeat the same with the 4th leaf too .

Mix the batter slightly. if required add water but take care that it should not be too thin . Meanwhile prepare a steamer

Pour the batter in the prepared kotte .cover with a lid and steam the idlis.

In case you feel making kotte is too time consuming but want to enjoy the fragrance of jackfruit leaves in the kadubu .. you can just place 4 leaves inside a tumbler and do kadubu. If you don't have jackfruit leaves .. you can still do kadubu by just filling the batter into a greased tumbler

Place the filled kotte inside a steamer / pressure cooker ( don't use weight) . Take care that the kotte kadubu stays upright while steaming .Steam cook for 20-25 mins on a medium flame till they are cooked . When a tooth [rick is pricked .. it should come out clean .

Take out the kotte kadubu from the steamer and allow to cool for 4-5 mins . Slowly remove the sticks and peel out the leaf .

Serve hot kotte kadubu along with chutney / sambar / majjige huli etc