In a mixer jar, add 1 cup leftover green moong sabzi, ½ cup besan, ½ cup rice flour, and ½ cup water. Grind everything into a thick batter. Do not add more water while grinding, as the batter should remain thick.
Transfer the batter to a mixing bowl and whisk it continuously for 3–4 minutes until it becomes light and fluffy.
Add ¼ cup finely chopped onion, 2–3 chopped green chilies, 1 tsp ginger paste, salt to taste, ½ tsp ajwain, 1 tsp fennel seeds, 1 tsp coarsely crushed black pepper, ¼ tsp baking soda, 1 tsp lemon juice, and some finely chopped coriander leaves. Mix everything well. The batter is now ready for frying.
Heat oil for deep frying. Using your fingers and thumb, carefully drop small portions of the batter into the hot oil.
Keep the flame high initially so the vadas hold their shape. Then reduce the flame to medium and fry until the vadas are golden brown and crispy on all sides.
Serve these hot and crispy Instant Dal Vadas with sliced onions, fried green chilies, and a cup of tea.