Preheat oven to 350 degrees. Slice squash lengthwise in half, removing seeds. Place squash, cut side down, in 12 x 18-inch baking dish. Bake 45 minutes. Prepare rice according to package directions. Cook sausage over medium heat until well browned, stirring frequently. Drain sausage well and place in a medium bowl. Toss sausage with egg, mushrooms, brown rice and syrup. Turn squash, cut side up, in baking dish and sprinkle with salt. Divide sausage mixture equally between the squash halves. Cover with foil and bake about 15 minutes at 350°, or until squash is tender.