Heat your deep fat fryer or a small pot filled with oil to 170°C (340°F). Use an electric probe thermometer to check the oil temperature accurately.
In a large bowl, combine sliced onions, potato matchsticks, green chilli, garlic ginger paste, fresh coriander, salt, and spices. Mix thoroughly to ensure the onions are well coated.
Crack one egg into the bowl and blend it well with the onion mixture, ensuring an even distribution.
Gradually add the chickpea flour, stirring constantly. Mix until there are no dry patches of flour. (Tip: Allow the mixture to rest for 10-15 minutes before frying, to enhance the texture and flavor.)
With gloves on, gently form a small portion of the mixture into a ball (1tbsp), avoiding over-compression. Carefully place it into the hot oil.
Fry each bhaji until golden-brown, flipping halfway for even cooking. Remove from oil with a spider strainer or tongs and drain on kitchen paper.
Continue frying the remaining bhajis. Serve warm, or reheat in the oven if necessary before serving.