Combine 150 g chickpea flour, the batter spice, 18 g green chilli, chopped coriander leaf to taste, and salt to taste in a large bowl. Gradually stir in enough water to form a thick, lump-free batter.
Pour vegetable oil into a kadhai or heavy, deep saucepan and heat to 180°C/350°F (a small cube of bread dropped in should brown within 30 seconds).
Working in small batches, dip 450 g onion slices into the batter until well coated, then carefully drop them into the hot oil. Fry for roughly 2 minutes until evenly deep golden and crisp.
Retrieve the fritters with a slotted spoon and drain on paper towels.
For crisping batters or binding cutlets: use 50% to 60% of the weight. Produces a very crisp shell but lacks the earthy, roasted nutty flavour of besan.
Use 80% of the weight, finely shredded and browned slowly with a pinch of asafoetida. Replicates the bulk and natural sweetness in gravies without allium.