Preheat your oven to 400 degrees. While the oven heats up, line a baking sheet with parchment paper to make cleanup easier.
Carefully scoop out the seeds and stringy center part from the spaghetti squash using a spoon. You can discard these or save the seeds for another recipe.
Place the squash cut side up on the baking sheet. Brush the flesh generously with olive oil and sprinkle with salt and pepper. Flip the squash upside down and roast.
Bake in the preheated oven until the squash is tender, which should take about 40 minutes. You’ll know it’s ready when you can easily pierce it with a fork.
Once baked, let the squash cool slightly. Using an oven mitt for safety, shred the spaghetti squash with a fork, leaving about a 1/4-inch border to form “boats.”
Return the empty squash halves to the baking sheet. In a large sauté pan over medium heat, melt the butter.
Add the minced garlic and flour into the pan and sauté for about 1 minute. You want the garlic to become fragrant but not browned.
While whisking vigorously, slowly pour in the half and half. Continue to cook, stirring constantly, until the mixture thickens slightly, about 3 to 5 minutes.
Reduce the heat to low and add in the parmesan cheese, stirring until it melts into a creamy sauce. If the mixture seems too thick, add in a splash or two more of half and half. Season to taste with salt and pepper.
Remove the pan from heat and fold the shredded spaghetti squash and 3/4 cup of mozzarella cheese into the creamy mixture until well combined. Taste again to check the seasoning.
Divide the cheesy mixture evenly among the squash halves, then sprinkle the remaining mozzarella cheese on top.
Return the squash to the oven and bake until the cheese is melted and bubbly, about 10 minutes.
Once out of the oven, sprinkle with minced parsley for a pop of color and serve warm. Enjoy!
