Cut the beef into 4 large chunks to ensure even cooking in the slow cooker. Trim off any large pieces of excess fat to prevent the sauce from becoming overly greasy.
Heat olive oil in a large skillet over medium-high heat. Sear the beef pieces for about 5 minutes per side until deeply browned. This step builds rich flavor. Transfer the seared beef to a 6-quart slow cooker.
In the same skillet, add a little more oil if needed. Sauté the minced garlic for 30 seconds until fragrant, then add the chopped onion and cook until soft and translucent, about 3 to 4 minutes.
Transfer the garlic and onion mixture into the slow cooker with the beef. Add the crushed tomatoes, tomato paste, beef broth, red wine, bouillon, italian herbs, bay leaves, salt, black pepper, and a pinch of a sugar. Stir to combine.
Cover the slow cooker with a lid and cook on LOW for 7-8 hours or HIGH for 4-5 hours, until the beef is fork-tender and easily pulled apart.
If you prefer a thicker sauce, stir together 1 tablespoon of cornstarch with 2 tablespoons of water and add it to the slow cooker. Cover and cook on HIGH for additional 30 minutes.
Remove the beef chunks from the slow cooker and shred using two forks. Discard any fatty bits, then return the shredded meat to the sauce and mix it until fully coated and evenly distributed.
Serve the rich beef ragu over pasta, creamy polenta, mashed potatoes, or zucchini noodles. Finish with a sprinkle of Parmesan cheese or fresh herbs like parsley or basil if desired.
Notes
IF SERVING WITH PASTA: In the last 15 minutes of cooking time, boil pasta in salted water following packet instructions. Drain, reserving 1/2 cup pasta water. Pour the reserved water back into the pasta along with 2 cups of cooked ragu. Stir until the sauce is thick enough to coat the pasta. Serve with parmesan cheese and (extra) chopped parsley, if desired.