1. Bring water to a boil.
2. Place farina in a bowl and add water, stirring to make a dough.
3. Add onion, chilies, salt, coriander leaves, cashew nuts, yoghurt, and ginger root and mix well.
4. Take 2 tbsp of dough mixture and make a thick, round patty. Cut with a doughnut cutter or use fingers to make a hole in center of patty.
5. Repeat with remaining dough.
6. Heat vegetable oil to 375 degrees F. Fry about 3 to 4 vadas at a time for 8 to 10 minutes, turning as necessary, until light brown.
7. Drain on paper towel. Serve hot with chutney.