For the filling, mix the coconut, cilantro, onions, chilies, sugar, and salt and set aside.
Prepare the tempering by heating the oil in a small pan on medium-high heat. When the oil is hot, add mustard seeds. As soon as the mustard seeds stop popping, turn the heat off and add asafoetida. Set aside to cool. When cooled, pour it over the filling and gently mix it.
Prepare a flat surface for spreading the batter. The backs of baking trays or a clean kitchen counter work well. We have always used large stainless-steel plates from India.
In a heavy-bottomed pan, mix the besan, yogurt/water mixture, additional water, turmeric, and salt together. Remove any lumps by using a wire whisk. Place the pan on your cooking stove and begin cooking on medium heat. Keep whisking continuously to prevent any lumps from forming as well as preventing the batter from sticking to the bottom of the pan. In about 7-10 minutes, the batter will start thickening. You will notice that the batter will have a slight shine. Immediately after this shine forms, test the batter by lifting a spatula full of batter. The batter should fall like a thick ribbon. At this stage, turn the heat to its lowest and work through the next step quickly.
Take about half a cup of the batter and spread with a small bowl, a round spoon, or with your hands over the prepared surface. The batter should be spread thinly and evenly. Do the same with rest of the batter quickly and let it cool for a few minutes. Spreading all the batter quickly is crucial otherwise it is impossible to spread the batter.
Sprinkle the filling over the spread batter evenly. Cut the spread batter into equally sized strips (about 2 inches wide and 7 inches long). Gently lift the end of the strip closest to you and start rolling away until the end of the strip. If you prefer to garnish over the rolls, make some extra filling. Serve it at room temperature.
