Sweet potatoes with chilli and cinnamon butter

Beat the butter until it's very soft, then stir in the chilli and cinnamon. Scoop butter out on to a small piece of baking parchment, then form the butter into a log shape, rolled up in the parchment. Chill until firm. Put the potatoes in a large pan of water and bring to the boil. Reduce the heat and simmer for 10-15 mins, then drain. Wrap the potatoes individually in foil and cook them on the barbecue for 20-30 mins, turning them occasionally, until they are very tender. Cut the butter into 6 slices. Remove the potatoes from the barbecue and cut a slit or cross in each one. Place a slice of butter onto each potato. Serve immediately, or re-wrap them in the foil to keep warm.