In a medium bowl, combine the turkey, 1/4 cup of the finely diced onion, egg, 2 minced garlic cloves, 1 1/2 teaspoons of the fresh oregano or parsley, mushrooms, and optional parmesan cheese and breadcrumbs if using. Add a little salt and pepper, and using your hands, mix thoroughly. Set aside.
In a small saucepan, simmer 4 smashed garlic cloves in 1 tablespoon olive oil. When it becomes fragrant, remove it from heat and add it to the slow cooker.
Add tomatoes, tomato paste, bay leaves, red wine, any leftover onions, thyme, basil, salt and pepper to the slow cooker and stir to combine.
Form turkey mixture into golf ball-sized meatballs, and place in a slow cooker. “Nestle” them in a little bit, so they touch the bottom of the slow cooker. They should form a single layer.
Cook on HIGH for 2.5 hours or on low 4 to 6, depending on your slow cooker. When the meatballs are cooked through, it’s done.
If you would like to serve over spaghetti squash (highly recommended, it’s SO good!) about an hour before dinner, have your oven pre-heated to 375°F. Cut open squash the long way, and scoop out seeds. Season the cut sides with 1/4 teaspoon salt. Place them cut sides down in a baking dish with about 1/- inch of water in it. Bake for about 45 minutes or until tender. Remove from the oven and baking sheet, and allow to cool. Cut sides up on a cutting board or some other surface until they are cool enough to touch. You want them still to be warm for the best taste. Scrape the flesh of the squash into strands using a fork. Let drain, and keep covered to keep warm in a colander over a bowl, or serve immediately.TIP: While the oven is on, you could add some other vegetables to roast. Just toss with olive oil and salt and pepper, and lay on a baking sheet in a single layer. Most vegetables take between 25-45 minutes. We’ve done green beans, asparagus, cauliflower and many other kinds this way!
Divide squash (or pasta) and meatballs with sauce onto plates. Sprinkle with parmesan cheese if desired.