Preheat the oven to 400F. Line a baking sheet with foil or parchment.

Slice the spaghetti squash in half lengthwise and scoop out the seeds and stringy bits. Spray the inside of the squash with cooking oil spray, and sprinkle with salt and pepper.

Place the spaghetti squash, cut side down, on the baking sheet and use a fork to poke holes all over it. Roast for 30-40 minutes, or until lightly browned on the outside and mostly fork tender.

In the last 10 minutes of the roasting time, melt butter in a skillet set over medium heat. Add garlic and cook for 30-60 seconds, until fragrant. Whisk in flour, and cook for 2 minutes. Gradually stream in milk, and whisk until smooth. Gently simmer until thickened, 3-4 minutes. Whisk in Parmesan, lemon juice, Italian seasoning, and salt and pepper to taste. Add spinach and stir, allowing it to wilt, then remove from heat and fold in shredded chicken.

Remove the spaghetti squash from the oven and, when it’s cool enough to handle, use a fork to scrape out all of the spaghetti-like strands. Stir them into the alfredo mixture.

Place the hollowed out squash boats back on the baking sheet and divide the mixture evenly between them, then sprinkle mozzarella cheese over the top. Return to the oven and bake for 10 minutes, then broil on high for 1-2 minutes, or until the cheese is golden brown. Serve garnished with fresh parsley.