Set the oven at 200C/gas mark 6. Trim the rhubarb stalks, removing the white “heel” at the base.
Cut the stalks into short pieces, about the size of your thumb, then put them in a shallow, ovenproof dish in a single layer.
Mix together the orange juice and honey, then add the star anise. Pour the mixture over the rhubarb then bake for 25 minutes until completely soft and tender.
While the rhubarb bakes, put the orange zest in the bowl of a food processor with the caster sugar and mint leaves, then process until the sugar is bright green.
Serve the rhubarb warm, with a little of the mint and orange sugar on top, spooning over the warm, honeyed juices as you go.