Position the rack of your oven in the middle and preheat it to 350 degrees.

Scrub the potatoes under cold, running water. Dry the skins well. Take a fork and pierce them 8 – 10 times, sticking the fork in as far as you can get it. Place potatoes in a large mixing bowl on a plate and pour on some olive or vegetable oil. Turn the potatoes round and round to totally coat them then sprinkle with a generous amount of kosher salt. Place the potatoes directly on the rack of the oven (you can place a baking sheet on the rack below the potatoes to keep the oil from dripping) and bake for 1 hour or until the skins feel crispy and the flesh yields to a gentle squeeze. Remove potatoes from the oven and let them cool enough to handle. Leave the oven on.

While the potatoes are baking, heat the olive oil in a large skillet over medium-high heat. Add the onions, mushrooms, ¾ teaspoon salt and ½ teaspoon pepper and cook for 10 minutes or until the vegetables are soft, the liquid from the mushrooms has been released and evaporated, and the vegetables are starting to brown.

Slice the potatoes in half lengthwise and scoop out the flesh into a mixing bowl, leaving a ¼ inch layer of the flesh in the potato skins. Mash the potatoes with a little salt and pepper and place the potato skins on a baking sheet.

To the mashed potatoes, add the mushroom onion mixture, the Horseradish sauce, vegan sour cream and about ¼ cup of the chives. Mix well. Taste and season with more salt and pepper if necessary. Spoon the mixture into the potato skins and bake for 15 minutes or until hot and the tops are starting to brown.

Sprinkle the remaining chives on top of the potatoes and serve.