Put ginger in a bowl and add rice.
Heat sufficient oil in a kadai.
Finely chop green chillies and add to the bowl. Finely chop coriander leaves and add to the bowl. Add salt, ½ tsp red chilli powder, ½ tsp cumin powder and ¼ tsp black salt and mash as you mix. You can also mash it in the mixer.
Shape the mixture into round balls and flatten them slightly. Gently slide them into hot oil and deep fry till crisp on the outside. Drain on absorbent paper.
Put the curd chillies into the hot oil and deep fry till crisp. Drain them on absorbent paper.
Put the yogurt in a large bowl, add salt and 1 tsp black salt and whisk together till well blended.
For tempering heat mustard oil in a non-stick pan.
While the oil is getting hot, for each portion put 3-4 tbsps yogurt in serving bowls, arrange some fried wade over it. Put some more yogurt over the wade.
When the oil is hot add cumin seeds, fenugreek seeds, curry leaves, ¼ tsp red chilli powder and ¼ tsp cumin powder and mix. Switch off the heat and pour the tempering over the wades in the serving bowl.
Crush 1-2 fried curd chillies and sprinkle on top. Garnish with a small sprig of fresh coriander leaves and serve immediately.