Wash and soak vatana in three cups of water for at least 8 hours. After soaking vatana will be about 2 1/2 times the volume of the original.
Put the vatana in a pressure cooker with 2½ cups of water. When the pressure cooker starts to steam, turn the heat down to medium and cook for 10 minutes. Turn off the heat and wait until steam has stopped before opening the pressure cooker. Vatana should be soft and tender. I have used instant pot, because it is more convenient.
Blend cilantro, green chilies, and ginger, tamarind chutney, and lemon juice.
Mix cilantro paste and all the spices, salt, black salt, sugar, black pepper and finely chopped green chili this is optional, to boiled vatana mix the spices well. This is known Ragda. Add hot water if needed Ragda should not be very dry it should have thick gravy, Ragda thickens in consistency as it cools.
For serving, make a small hole on top of each puri and arrange them on a platter. Stuff them with the ragda. Drizzle with tamarind chutney and sev.