If using ground beef or sausage, brown it in a skillet on high heat

Rinse squash and pat dry

Using a very sharp knife, carefully cut the squash in half crosswise

Using a spoon, scrape centers of the squash to remove seeds

Add squash, cut side down, to a casserole-style slow cooker

Check to ensure the lid will close; if not cut squash pieces in half again

Around the squash, add sausage; if using meatballs cut in half or quarters

Add the remaining ingredients to slow cooker

Cook on high for 3 hours or low for 6 hours

Turn off cooker and carefully remove cooked squash with heavy tongs or/or pot holders and let cool for a few minutes

See note below about final broiling

Using a spatula, carefully scrape the slow cooker to dislodge any meat from the bottom

Using a fork, comb the squash pulp out of the skins - allowing it to shred into spaghetti-looking

Add shredded squash back into the slow cooker and carefully fold into the sauce and meat

Fold 1/2 cup of both cheeses into the spaghetti

Sprinkle the remaining 1/4 cup Parmesan on top

Final Broiling (optional, reference note below): Broil on high (with oven door open) for 3-5 minutes or until Parmesan has bubbled and began to brown slightly - if using grated Parmesan from the jar, you'll get a bit of snap-crackle-pop from it