Preheat the Oven: Preheat your oven to 400°F (200°C).
Prepare the Spaghetti Squash: Halve the spaghetti squash lengthwise. Scoop out the seeds and stringy pulp. Brush the insides with 1 tablespoon of olive oil and season with salt and pepper. Place the squash cut-side down on a baking sheet lined with parchment paper.
Roast the Spaghetti Squash: Roast in the preheated oven for about 30-40 minutes, or until the flesh is tender and can be easily shredded with a fork. Once cooked, remove from the oven and let cool slightly.
Sauté the Mushroom Mixture: In a large skillet, heat the remaining tablespoon of olive oil over medium heat. Add the chopped onion and sauté until translucent, about 3-5 minutes. Stir in the minced garlic and cook for an additional 1-2 minutes until fragrant.
Add Mushrooms and Herbs: Add the diced mushrooms, dried thyme, oregano, and red pepper flakes (if using). Cook for about 5-7 minutes, until the mushrooms release their moisture and become golden. Season with salt and pepper to taste.
Combine with Cheese and Herbs: Remove the skillet from heat. Stir in the chopped parsley, ricotta cheese, and grated Parmesan cheese until well combined.
Stuff the Squash: Once the spaghetti squash is cool enough to handle, use a fork to scrape the insides into strands. Leave some strands intact to form a bowl. Fold the spaghetti squash strands into the mushroom mixture until evenly incorporated.
Fill the Squash: Spoon the mushroom and spaghetti mixture back into the squash halves. Top each half with a sprinkle of breadcrumbs and shredded mozzarella cheese.
Bake the Stuffed Squash: Return the stuffed squash to the oven and bake for an additional 15-20 minutes, or until the cheese is melted and bubbly, and the breadcrumbs are golden.
Serve and Enjoy: Remove from the oven, let cool for a few minutes, then slice and serve warm. Garnish with additional parsley if desired.
Notes
Feel free to adjust the herbs and seasonings to your taste.