Peel and grate dudhi with medium size grater. Keep it aside.
Now in a pan, add 1 cup of water, oil, while sesame seeds, ajwain, salt, green chili paste and ginger paste. Mix well.
Then add grated dudhi (lauki) and mix well. Cover and cook on a medium flame for 3-4 minutes or till dudhi become slightly soft.
Now add rice flour gradually and mix well. The mixture is slightly crumbly; do not add more water to it.
Cover and cook mixture for 1-2 minutes on low flame.
Now switch off the gas and add the cooked mixture into the mixing bowl.
Add coriander leaves and slightly grease hand with oil and knead dough when the mixture is slightly hot.
Then make medium size ball from the dough and roll it into a medium thick roti. Do not roll it thin.
Cut nasta into small and medium thick rounds. Make all into the same way.
Now heat oil in a pan, add vada, and deep-fried on medium-low flame.
Take out fried vada on a wire rack or tissue paper and serve with chutney.