Finely chop onions and put them in a bowl. Add little salt and mix the onions well so that it becomes soft. In the same bowl, add crushed green chillies, cumin seeds, hing, chilli powder and pinch of garam masala, ajwain, broken coriander seeds, cooking soda and mix it well. In this add enough besan (chickpea flour) and mix well to make soft dough. Heat oil in a kadai and when the oil is hot, drop the onion bhajias in batches and deep fry on medium flame until they are crisp and turn golden in colour. Remove, drain oil and serve hot as starters or snack.