1- In a mixing bowl, combine besan, yogurt, water, turmeric powder, ginger paste, green chili paste, and salt. Whisk until the mixture is smooth and free of any lumps.
2- Pour the mixture into a non-stick pan and cook over medium heat, stirring continuously to avoid lumps, until the mixture thickens and starts leaving the sides of the pan. This should take about 7-10 minutes.
3- Once the mixture is cooked, quickly pour it onto the back of a greased plate or a clean kitchen counter. Using a spatula, spread the mixture into a thin, even layer.
4- Let the mixture cool for a few minutes. Once it’s cool enough to handle but still warm, cut it into thin strips using a knife.
5- Carefully roll each strip into a tight roll and place them on a serving platter.
6- In a small pan, heat oil over medium heat. Add mustard seeds and let them splutter. Then add sesame seeds and asafoetida. Cook in hot oil until it becomes aromatic.
7- Pour the tempering over the rolled khandvi.
8- Garnish with freshly chopped coriander leaves and grated coconut if desired.
9- Let the khandvi cool down completely before serving.
10- Serve the delicious khandvi as an appetizer or snack, and enjoy!