1. For Sour Water: In a blender put together ginger, mint leaves, green chilies and blend to a fine paste.
2. Mix in water with tamarind pulp, lemon juice, roasted cumin, roasted coriander powder, chili powder and salt, mixes well.
3. The water should be tangy and spicy. Strain water and keep in the fridge to chili or add ice and use.
4. For Gol Gappa: In bowl mix together semolina, flour, white lentil, knead with club soda to from stiff dough.
5. Keep aside for 30 minutes, and then knead once again.
6. Make marbles size balls with little oil on your hands, roll out into puri with a rolling pin, secure between two layers of wet cloth, roll out all of them and leave aside for 10 minutes.
7. Deep fry on medium heat till they puff up, reduce heat and fry till crisp.
8. To Assemble: Puncture the Gol gappa with tip of your thumb, add 1 tsp of filling and top it with the sour water, if you like it a little sweet add little sweet tamarind or plum chutney before adding the water.