Mix the onions, spinach, chickpea flour, ginger, ground coriander seeds and green chilli together with enough water to bind into a thick batter mixture.
Add the salt, chilli powder and turmeric and mix thoroughly.
Heat the sunflower oil in a wok for frying. The oil should come about 2.5cm (1 inch) up the sides of the wok.
Gently drop a little of the bhaji mixture into the hot oil to test it's hot enough.
When ready, place golf-ball sized amounts of the mixture into the oil. Reduce the heat and fry gently until golden in colour.
Remove from the oil and drain on kitchen paper.
Increase the heat of the oil and return the cooked bhajis to the wok and fry for a second time until crisp and golden brown.
Sprinkle with chaat masala, if you like, and serve.