Heat the oil in a saucepan, add the onion and fry, stirring, until pale golden. Mix in the remaining vegetables and fry for 2–3 minutes. Stir in the turmeric and curry paste, then add the lentils and stock.
Add the chicken and seasoning, then bring to the boil. Cover and simmer for 40 minutes, stirring occasionally, until the vegetables and lentils are softened.
Ladle into bowls and sprinkle with torn coriander leaves. Serve with warm naan breads.