1. Preheat your oven to 400 F (200 C). Carefully cut the spaghetti squash in half lengthwise and scoop out the seeds and stringy bits. Drizzle the cut sides with a little olive oil, season with a pinch of salt and pepper, and place cut-side down on a baking sheet. Roast for 30-40 minutes, or until tender enough to easily shred with a fork. You’ll know it’s ready when the flesh is soft and pulls away easily.

2. While the squash is roasting, heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the chopped onion and cook for 5-7 minutes until softened and translucent. Stir in the minced garlic and cook for another minute until fragrant.

3. Add the fresh spinach to the skillet with the onions and garlic. Cook, stirring frequently, until the spinach has completely wilted, which usually takes about 2-3 minutes. Remove the skillet from the heat.

4. Once the spaghetti squash is cooked, remove it from the oven and let it cool slightly until it’s comfortable to handle. Using a fork, scrape the strands of squash into a large mixing bowl. It should resemble spaghetti.

5. Add the cooked and shredded chicken, the wilted spinach and onion mixture, cream of mushroom soup, milk, 1/2 cup of Parmesan cheese, and black pepper to the bowl with the spaghetti squash. Stir everything together until well combined. Taste and add a pinch more salt if needed.

6. Transfer the mixture into a 9×13 inch baking dish, spreading it evenly. Sprinkle an additional layer of Parmesan cheese (or your preferred cheese) over the top.

7. Bake for 20-25 minutes, or until the casserole is bubbly around the edges and the cheese on top is melted and lightly golden brown. Let it rest for a few minutes before serving.