Preheat oven to 350 degrees F (175 degrees C). Place the squash halves cut sides down into a baking dish, and pour in enough water to cover the bottom of the pan.
Bake in the preheated oven until the squash is tender, about 30 minutes.
While the squash is baking, bring 2 cups of water to a boil in a saucepan over medium heat, and stir in the margarine and the contents of the rice package. Reduce heat to a simmer, and cook until rice is tender, about 7 minutes. Set the prepared rice aside.
Heat a large skillet over medium heat, and cook the sausage, mushrooms, coriander, and salt (if needed) until the sausage is browned, about 10 minutes. Drain excess grease. Mix the sausage mixture with the cooked rice mixture in a bowl, and lightly stir in the apple, pecans, and Cheddar cheese.
Pour melted butter into a baking dish, and place the squash, hollow sides up, into the dish. Stuff the rice and sausage mixture into the squash, allowing the stuffing to mound up and overflow into the dish if necessary. Sprinkle the stuffed squash with Parmesan cheese.
Return to oven, and bake until the stuffing is hot and the cheese topping has browned, about 30 more minutes.
