Heat the oil in a saucepan and fry the onion, with the lid on, until softened.

Stir in the garlic and ginger and leave uncovered to fry for another 2 minutes.

Stir in the spices.

Boil the kettle.

Add the tomato purée, soy sauce, peanut butter, coconut milk and 200ml boiling water.

Whisk while bringing to the boil and then add the sweet potato chunks.

Turn down the heat and cook uncovered for 15–20 minutes until the potato is soft and the sauce has thickened.

If the sauce has reduced enough but the potato is not tender yet, partly cover with the lid.

Stir in the kale and cook for 1 minute.

Taste and season with lime juice, salt and pepper.