1. Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
2. Cut the spaghetti squash in half lengthwise and scoop out the seeds. Drizzle the insides with olive oil and season with a pinch of salt and pepper.
3. Place the squash halves cut-side down on the baking sheet. Roast for 40 minutes, or until the flesh is tender and easily shredded with a fork.
4. While the squash is baking, heat olive oil in a skillet over medium heat. Add the chopped onion and cook until translucent, about 5 minutes. Stir in the minced garlic and cook for another minute.
5. Pour in the heavy cream, bringing it to a gentle simmer. Stir in the Gruyère and Parmesan cheeses, allowing them to melt into a smooth sauce. Season with salt, pepper, and nutmeg. Remove from heat.
6. Once the squash is done, use a fork to scrape the flesh into spaghetti-like strands. Transfer the squash strands to a large mixing bowl.
7. Add the cheese sauce to the squash strands, mixing well to combine. Transfer the mixture into a greased baking dish.
8. Top with additional Parmesan cheese, if desired. Bake in the oven at 400°F (200°C) for 15-20 minutes, or until the top is golden and bubbly.
9. Garnish with fresh parsley before serving for a pop of color and freshness.

Remember, cooking is all about patience and enjoying the process. My grandmother always said the best meals come from taking your time to savor each step.