Heat the oil in a large saucepan and fry the onions for 5 minutes until beginning to colour. Stir in the curry paste and then the tomatoes, chickpeas, stock and sugar.
Bring to the boil, then reduce the heat, cover and simmer gently for 20 minutes.
Stir in the kale and cook gently for a further 10 minutes. Season to taste with salt and pepper and serve.