1. Preheat your oven to 375°F.

2. Prepare the pumpkin by cutting off the top and scooping out the seeds and fibrous bits.

3. In a skillet, heat the olive oil over medium heat. Sauté the diced onion and minced garlic until soft and fragrant.

4. Add the chopped mushrooms to the skillet and cook until tender.

5. Incorporate the fresh spinach and stir until wilted. Season with salt and pepper.

6. Stuff the mushroom and spinach mixture into the hollowed-out pumpkin. Optionally, sprinkle grated cheese on top.

7. Place the stuffed pumpkin on a baking sheet and bake for 45-60 minutes, or until tender and filling is bubbling hot.

8. Let it rest for 5 minutes before slicing and serving warm.