Place the potatoes on a foil-lined baking sheet, whole with the skin on, and roast for 50 minutes to 1 hour (depending on the size), or until soft and the peels are papery and pulling away from the flesh. Cool until you can easily peel the jackets from the potatoes, then discard the peel.
Reduce the oven temperature to 350°F. Add all of the ingredients to the food processor and whip everything together until smooth (you can do this in batches if necessary).
Butter 6 large ramekins and carefully pour the mixture into each, being careful not to over-fill. Place ramekins on a sheet pan and bake in oven for about 40 minutes (when done, the soufflés should jiggle slightly).
Adapted from Cooking Light, September 1996While I bake the soufflé in individual ramekins, a baking dish works well for passing round to your lovely dinner crowd. If you choose the ramekin route, fill them quite full, the soufflé does deflate quite a bit upon cooling.This would be excellent served with a crème fraîche or sour cream-spiked whipped cream, as well as some toasted pecans!