1. Preheat oven to 400°F (200°C).

2. Slice spaghetti squash lengthwise and remove seeds. Drizzle with olive oil and roast cut-side down for 35–40 minutes until tender.

3. Allow squash to cool slightly, then shred flesh with a fork and transfer to a large bowl.

4. In a skillet over medium heat, sauté onion and garlic in olive oil until translucent.

5. Add spinach to the skillet and cook until wilted, then stir in diced chicken.

6. Combine the chicken-spinach mixture with shredded squash, cream or Greek yogurt, Italian seasoning, half of the cheese, salt, and pepper.

7. Transfer mixture to a greased baking dish and spread evenly.

8. Sprinkle remaining cheese on top and bake at 375°F (190°C) for 20–25 minutes until golden and bubbly.

9. Let the casserole rest for 5 minutes before serving.