Pierce each potato a couple of times with a skewer and place on a baking sheet. Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 45 minutes until very soft. Leave until cool enough to handle, then use a spoon to scoop out the flesh.
Heat the butter, orange rind and juice in a saucepan until the butter is melted. Remove from the heat and add the sweet potato flesh and chipotle paste, then mash until smooth. Season well.
Transfer the mash to a serving dish, spoon over the soured cream and serve.