Rinse and grind the ginger and garlic together to a fine paste. Blanch the methi leaves in boiling water and refresh with cold, running water. Add some salt to the chopped onions and cook them in their own juices, until they are translucent (fry them without oil). Add the methi leaves and sauté. Add ginger-garlic paste and continue to sauté for a minute more. Add red chilli powder and green peas. Cook for three to four minutes. Add dry mango powder, cinnamon powder and salt. Mix well. Cook for two to three minutes. Blend the cashew butter with ⅓ cup water until you obtain the consistency of cream. Add this to the cooked vegetables and serve warm.