Pierce the spaghetti squash with sharp knife 8-10 times all around.
Place the squash in the bowl of your slow cooker. Cover and cook on HIGH 3-4 hours or LOW 6-8 hours.
One the squash is tender, remove from the slow cooker and allow to cool.
Once the squash is cool, slice lengthwise and scoop out the seeds with a spoon.
Using a fork, scrape the flesh inside the squash to create long strands (like noodles).
Return the flesh to the slow cooker and turn it on low.
Add cream, garlic and butter and stir to combine. Continue to cook on low, stirring occasionally until the sauce thickens and is creamy.
Add in the Parmesan cheese and stir to combine. Season with salt and pepper if you choose.