
In a large skillet over medium heat, heat oil. Add onion, carrot, celery, and garlic and cook until tender, 6 minutes. Add tomato paste and stir until combined, then add ground beef and cook until no longer pink, 6 to 8 minutes. Transfer mixture with a slotted spoon to slow cooker.
Add crushed tomatoes, oregano, thyme, bay leaf, salt, milk, and red wine. Season with pepper and stir until combined.
Cover and cook on low for 6 hours. Discard bay leaf.
Serve over cooked pasta.