Whisk gram flour and yogurt till smooth. Add 2 cups water and whisk again. Heat oil in a non stick pan. Grind together green chillies, 10-12 spinach leaves and ginger with a little water to a fine puree.
Add this to the yogurt mixture and mix well. Add red chillies to the oil in the pan and sauté. Cut the onion into small cubes. Add mustard seeds and cumin seeds to the pan along with onion and sauté till the onion softens.
Add yogurt mixture, salt, turmeric powder and mix. Cook on medium heat, stirring, till the gram flour gets cooked and the kadhi thickens. Chop remaining spinach leaves and add to the kadhi and simmer for a couple of minutes. Serve hot.