Preheat the oven to 500 degrees F. Lay the potatoes lengthwise. Carefully scoop out the insides and transfer to a bowl. Add the cheese, sour cream, chives and arugula and mash with a fork. Season with pepper. Carefully stuff the potato mixture back into the the skings. Set on a baking sheet lined with aluminim foil abd bake for about 30 minutes longer, until heated through and lightly browned. Serve immediately.