Soak the urad dal in a bowl of water overnight.
The next day, drain the lentils, place them in a food processor, and process to make a smooth, stiff paste. Mix in the spices, ginger, and chopped coriander. Set aside.
Divide the poori dough into 10 equal portions and shape it into small balls.
Flatten the dough slightly, then put 1 level teaspoon of the paste into the center and fold the dough over to enclose the filling completely. Dust each ball with a little flour and, using a rolling pin, roll the balls out carefully into rounds.
Heat enough oil for deep-frying in a kadhai or deep, heavy-based pan to 180'C / 350'F, or until a cube of bread browns in 30 seconds.
Working in batches, carefully lower the pooris into the hot oil and deep-fry for 1-2 minutes, or until puffed up and golden brown. Remove with a slotted spoon and drain on kitchen paper (paper towels).