Place the whole sweet potatoes into a medium saucepan onto a high heat. Do not remove the skins as this will leach some of the purple pigment. (When I cook blue, purple or red potatoes, I always boil with the skins left on). Boil for 15 to 20 minutes until a fork enters the potato easily. Remove from the heat and drain the sweet potatoes. Peel them with your fingers when cool enough to handle. Slice into pound coin thick slices. Set aside to cool.

Prepare the oranges by peeling with a knife then segmenting. This technique is known as 'supreme' and you can look at Youtube videos to learn how. However if you can't be bothered to do that, you can also cut the potatoes and oranges into chunks, as in the picture above.

Mix the orange segments with the cooled sweet potatoes and add the juice of a lime. Add the salt, chilli and coriander. Toss and serve.