Position rack in center of oven and preheat to 425. Mince spinach stems and garlic in food processor. Melt butter in heavy skillet over medium low heat. Stir in garlic mixture and saute until spinach stems are very soft (about 8 minutes). Add whipping cream and simmer until reduced by half (about 5 minutes). Coarsely chop spinach leaves in processor in batches using off on turns. Add to cream mixture with nutmeg and pepper. Increase heat to high and cook until spinach is heated through about 3 minutes. remove from heat. Stir in scallops and pasta. transfer to shallow 4 quart baking dish. Sprinkle with reserved parmesan cheese over top. Bake until scallops are just opaque, about 10 to 12 minutes. Serve immediately.