Preheat the oven to 350˚F. Cut the spaghetti squash in half and scoop out the seeds. Brush both sides with olive oil and place cut side down on baking sheet.
Bake until tender, around 1 hour.
Once cooked, use a fork to scrape out the "spaghetti" strands into the centre.
In a small saucepan, melt the butter. Add in the garlic and cook for 1-2 minutes. Whisk in the flour for around 1 minute. Stir in the cream cheese. Whisk in the milk. Allow to simmer until thickened.
Remove from heat and mix in Parmesan until melted.
Divide the sauce into each spaghetti squash, and stir to combine. Sprinkle with additional Parmesan, and broil for 1-2 minutes. Serve immediately.