Prep the beef. Pat the beef dry with paper towels, then season generously with salt and pepper.
Toss with 3 tablespoons of flour to lightly coat.
Crisp the bacon. In a large skillet over medium heat, cook the chopped bacon until lightly crispy. Transfer bacon to the slow cooker, leaving some fat in the pan.
Brown the beef in batches. Add 1 to 2 tablespoons olive oil to the bacon fat if needed. Sear the beef on all sides until deeply browned.
Don’t crowd the pan. Transfer browned beef to the slow cooker.
Sauté aromatics. Add a little more oil if the pan is dry. Sauté the onion and carrots for 3 to 4 minutes, scraping up browned bits.
Stir in garlic and cook 30 seconds. Add tomato paste and cook 1 minute to caramelize. Transfer mixture to the slow cooker.
Deglaze with wine. Pour the red wine into the hot skillet and scrape up the fond.
Let it simmer for 2 to 3 minutes to reduce slightly. Pour into the slow cooker.
Add liquids and herbs. Stir in beef broth, Worcestershire, bay leaves, and thyme. Add mushrooms and pearl onions.
Cook low and slow. Cover and cook on LOW for 8 to 10 hours, or on HIGH for 4 to 5 hours, until the beef is very tender.
Finish the sauce. If you want a thicker sauce, whisk 1 tablespoon flour with 2 tablespoons water into a slurry and stir it in.
Cook uncovered for 10 to 15 minutes. For extra richness, stir in 2 tablespoons butter at the end.
Taste and serve. Remove bay leaves. Taste and adjust salt and pepper.
Garnish with chopped parsley.
Serve with something cozy. It’s classic with buttered mashed potatoes, buttered noodles, or crusty bread. Creamy polenta is also great.