Brush the peppers with olive oil inside and out and roast in an oven preheated to 180°C/350°F/gas mark 4 for about 30 minutes, or until completely soft. Put the peppers with their cooking juices into a blender with all the other ingredients for the cream. Blend until smooth. Chill until needed.
Heat the oil and butter in a saucepan over a low-medium heat and add t