Heat oil in a non-stick pan, add cashewnuts and pistachios and sauté till golden.
Chop jaggery. When the nuts turn golden, add jaggery and mix well. Switch off heat and add coconut, mix well and sauté. Add green cardamom powder and mix well. Transfer into a bowl and set aside.
Roughly chop mangoes and put into another bowl.
Put oats in a mixer jar and grind to a powder. Add mango pieces and grind. Add 1 cup water and grind again till fine. Transfer into a large bowl.
Add cornstarch. Rinse the mixer jar with ½ cup water and add it to the bowl and mix well.
Heat a non-stick pan, add a little oil and wipe it clean with a wet tissue paper in order to temper the pan.
Add sufficient water to the batter to adjust its consistency.
Put a ladle full of batter into the heated pan and rotate the pan in order to spread the batter evenly. Drizzle a little oil and rotate the pan again so that the oil goes all around the pan.
Cook till the underside is golden, flip the pancake over and cook for a couple of minutes.
Flip the pancake again, and spread a generous amount of the coconut filling on one side. Fold the other side over to make a half moon shape.
Transfer the pancake onto a serving plate and drizzle chocolate sauce over. Serve hot.