For preparing hyderabadi shahi dahi vada, first wash urad dal thoroughly and soak in water for 5 hours.
Grind urad dal to a fine paste. Add green chilly, ginger-garlic paste and required salt to the urad batter. Mix well.
Take a katori and cover the mouth with a tight wet cloth so as to retain a flat surface on top.
Take 1 tbsp of urad batter on top of wet cloth and flatten it with wet hands. Make a hole in the centre. Repeat making vadas with the entire batter.
Heat oil in a frying pan and slide each vada into the heated oil. Deep fry until golden brown on both sides.
Put the fried vadas in hot water for 3 minutes till soft. Squeeze out water by pressing vada between the palms of your hand.
Churn curd and salt together until smooth. Keep 1/2 cup of curd aside and add all vadas to the remaining curd.
Place hyderabadi shahi dahi vada in a serving dish along with the curd. Pour the remaining 1/2 cup curd on top.
Sprinkle cumin seed powder and red chilly powder on top and garnish with coriander leaves and tamarind chutney.