Soak the rice and lentils in 2 separate large bowls of water for 1 hour.
Drain the rice, transfer to a blender or food processor and process, gradually adding about 125ml / 4 1/2fl oz (1/2 cup) water to make a coarse batter. Transfer to a bowl.
Drain the lentils, transfer to a blender or food processor, add the ginger and chillies and process, gradually adding 250ml / 8fl oz (1 cup) water to make a coarse batter.
Combine both batters, then season with salt and add the curry leaves, coconut and a little more water, if necessary, to make a thick batter of pouring consistency.
Heat a tawa, flat griddle or frying pan (skillet) over high heat until it sizzles when a few drops of water are sprinkled on to it. Reduce the heat and smear a very thin film of oil evenly over the tawa.
Pour a ladleful of the batter into the centre of the tawa and spread it out quickly using a circular motion with the back of the ladle to form a 15cm / 6 inch round pancake.
Make a hole in the centre and drizzle 1 teaspoon oil around the edges and centre. Cook for about 2 minutes, or until the base is golden, then turn carefully with a spatula and fry the other side for a further 2 minutes, or until crisp and golden.
Transfer to a serving plate and serve hot. Make the others in the same way.