Heat the oil in a large, nonstick frying pan, add the onions, curry leaves and nigella seeds and stir-fry for 3 minutes.
Add the chilli and prawns and fry, stirring constantly, for 5–7 minutes. Add the ginger and salt and fry, stirring, for another minute or until the prawns turn pink and are just cooked through.
Finally, add the fenugreek leaves and lemon juice and cook for 1–2 minutes. Remove from the heat and serve hot with warmed white bread.