Cook all the potatoes, parsnips, carrots, and salsify in salted boiling water for about 30 minutes, or until tender. Add the inside of the potatoes to the rest of the vegetables. Mash the vegetables along with the cream and butter. Season the vegetables with salt, and pepper, to taste. Keep warm.
Preheat the oven to 350 degrees F.
Bake the potatoes until soft, about 40 minutes depending on the size.
Heat the oil in a deep fryer to 375 degrees F.
Remove the potatoes from the oven. Scoop out the flesh and transfer to a bowl for use in the Root Vegetable Mash, recipe follows. Place the potato skins into the fryer until they become brown and crispy. Remove the skins, place on paper towels and season with salt, and pepper, to taste. Let cool to room temperature.
Mix the crab with the mayonnaise, Dijon, green onions, and chives. Season the mixture with salt, and pepper, to taste. Spoon the mixture into the potato skins.