01 - Heat olive oil in a large skillet over medium heat. Add ground beef and sausage, breaking up the meat with a spoon, and cook until browned, about 6 to 8 minutes. Drain excess fat if needed.
02 - Add onion, carrots, and celery to the skillet. Sauté for 5 minutes until softened. Stir in garlic and cook for an additional minute.
03 - Transfer the meat and vegetable mixture to the slow cooker.
04 - Incorporate crushed tomatoes, tomato paste, red wine, broth, oregano, basil, thyme, bay leaf, salt, pepper, and optional red pepper flakes. Stir to combine evenly.
05 - Cover and cook on LOW heat setting for 8 hours, or on HIGH for 4 hours, stirring once or twice during cooking if possible.
06 - Remove the bay leaf. Stir in milk or cream and adjust seasoning to taste.
07 - Serve warm over cooked pasta, garnished with fresh parsley and freshly grated Parmesan cheese.