1. If using a conventional oven, bake the potatoes at 400°F for about 45 minutes, or until tender. If using a microwave oven, pierce each potato with a fork before microwaving on high power for about 15 minutes, or until tender. Set aside to cool.
2. Cut the potatoes in half lengthwise. Scoop out and discard the pulp, leaving a 1/4 inch-thick shell. Place 1 tablespoon of broccoli in each skin, and top with the cheese.
3. Place the potato skins on a baking sheet, and bake at 450°F for about 15 minutes, or until the cheese is bubbly. Transfer the skins to a serving platter, top each skin with 1 tablespoon of nonfat sour cream and a sprinkling of scallions.