In a large bowl combine beef stew meat, salt, pepper and flour. Toss until beef is well coated.
Heat the canola in a large saute pan over high heat. Add seasoned beef and sear on all sides until brown and caramelized. Remove to a plate and set aside.
Combine seared beef, carrots, mushrooms, potatoes and tomatoes in a 4-quart slow cooker.
In a medium bowl, stir together grated chocolate, garlic, meatloaf packet, beef broth, and red wine. Pour into slow cooker and sprinkle the leeks over the top. Cover and cook on HIGH setting for 4 to 6 hours.