In a microwave safe glass casserole, combine ginger, chilies, curry leaves and microwave for a minute on high power.
Add onions and mix well so that they are coated with oil.
Microwave for 6 minutes stirring the onions at intervals of every 2 minutes on high power.
Combine the idli rava with the onions and mix thoroughly.
Microwave again for a minute.
Add buttermilk and hot water to the mixture, stir well and microwave for another minute.
Remove casserole from microwave and serve the upma hot with cashews as garnish.