Preheat oven to 425°F. Cut squash in half lengthwise and scoop out seeds.

Spray the cut sides of the squash with oil and sprinkle with salt. Place face down on a baking sheet and bake for 20-25 minutes until tender.

Meanwhile, in a large skillet, cook sausage over medium heat, breaking it apart, until browned. Add chopped onion and celery, cook until soft, about 8-10 minutes.

Add chopped mushrooms and thyme to the skillet, season with salt and pepper if needed, cook for 5 minutes, then cover and cook for 2 more minutes until mushrooms are soft.

Remove squash from oven, stuff with the sausage mixture, top with parmesan cheese, and bake for an additional 10 minutes.

Garnish with chopped parsley and serve hot.