Pat beef dry with paper towels; sprinkle with pepper and salt. Heat oil in a large Dutch oven over medium-high heat. Add beef in batches and cook for 1 to 2 minutes or until browned. Transfer to a 6-quart slow cooker; set aside.

Cook bacon over medium heat in the Dutch oven until crisp. Transfer bacon to the slow cooker using a slotted spoon. Add onion and garlic to bacon drippings in Dutch oven. Cook for 2 to 3 minutes or until softened; transfer to slow cooker.

Remove Dutch oven from heat; add red wine. Return to heat; cook and scrape brown bits from bottom of Dutch oven. Whisk in beef bouillon and tomato paste until combined. Pour wine mixture over beef in slow cooker. Stir in pearl onions, baby bella and shiitake mushrooms.

Tie 8 sprigs of thyme together with kitchen string; add to slow cooker. Cover and cook on LOW for 7 hours. Remove and discard thyme bundle; add carrots. Cover and cook for 1 to 1½ hours more or until carrots are tender. Garnish with chopped fresh thyme, if desired. Serve with French bread, if desired.