Slice spaghetti squash in half lengthwise. Scrape out seeds. Place face down on a baking sheet. Bake in a preheated 375 degree oven for 30 minutes.
Remove from oven and let cool. Use a fork to remove the strands of squash and place into a bowl. Leave a small amount in the shell so the shell isn't too flimsy.
Place shells right side up on a baking sheet. Set aside.
Alfredo Sauce
In a sauce pot, add olive oil and garlic over medium low heat. Just heat the garlic through so it turns fragrant, but do not brown.
Add the heavy cream. Heat until just before the cream comes to a boil. Stir cream often to prevent scorching.
Whisk in Parmesan cheese. Add pepper and nutmeg. Taste to see if salt is needed. I often find the Parmesan cheese salty enough and don't add any additional salt.
Continue cooking over low heat, while stirring, until the sauce thickens slightly. Remove from heat.
Pour Alfredo sauce over strands of spaghetti squash. Stir so the sauce is evenly distributed.
Divide squash into two shells. Sprinkle with additional Parmesan cheese.
Level shells on tray with a coil of foil placed around the base of each shell. If the shells are not level, the sauce will spill out while baking.
Bake in a preheated 375 degree oven for 30-35 minutes until the sauce is bubbly and browned on top.