Add the vegetable oil to a deep-fat fryer and preheat to 180C. Alternatively, heat around 4–5cm/1½–2in oil in a deep saucepan. To test the oil is hot enough, carefully drop a little of the bhaji batter into the oil – it will sizzle once hot enough and start to brown. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Place the red onion in a large bowl and add the chopped coriander, chilli powder, turmeric, garam masala, ground coriander and cumin. Add the gram flour, garlic, ginger and a generous sprinkle of salt. Pour in approximately 75ml/2½fl oz cold water to bind. Mix well again to combine – the mixture should hold together once squeezed but it may be a little sticky. Add a touch more water if the mixture feels too stiff.
Using wet hands, roll the mixture into 12 small balls that are roughly the size of golf balls.
Deep-fry the bhajis in the hot oil in two batches for 3–4 minutes, until golden brown and crisp. Carefully remove using a slotted spoon and transfer to kitchen paper to drain. Sprinkle with a little salt and serve warm.
