Heat the oil in a large wok or frying pan over a medium heat. Add the curry leaves and stir-fry for 30 seconds. Add the shallots and stir-fry for a further 4–5 minutes.
Add the garlic, ginger and fennel seeds, reduce the heat and cook gently for 2–3 minutes. Sprinkle over the curry powder and add the tomatoes, including any juices. Increase the heat and stir-fry for 3–4 minutes.
Add the prawns and continue cooking over a high heat for 6–7 minutes until the prawns turn pink and are just cooked through. Remove from the heat, season to taste and serve immediately with rice or crushed sesame spiced potatoes.