Put a light cross-notch on the surface of the potatoes with a kitchen knife. Place the prepared potatoes on the low wire rack with glass dish underneath and select the weight 900g. The oven will tell you when to turn the potatoes over.
Whilst the potatoes are cooking, make the rocket pesto. Toast the cashews in a dry frying pan. Tip the cashews into a food processor, along with garlic, parmesan, extra virgin olive oil, and rocket leaves. Season with salt and pepper and blend till smooth. Transfer to a serving bowl and set aside.
When the potatoes are ready, cut a cross on top of each potato, squeeze the sides, add a dollop of sour cream to finish.