1. Start by heating olive oil in a large skillet over medium-high heat. While it warms, pat your beef roast dry with paper towels — this helps to get a nice brown crust.
2. Season the roast generously with salt and pepper on all sides. Then, sear the roast in the hot skillet, about 3-4 minutes per side, until it’s beautifully browned. This step locks in flavor, a trick Mama Lu swore by.
3. Remove the roast and set it aside. In the same skillet, reduce heat to medium and add the butter. Once melted, toss in the sliced onions and a pinch of salt. Cook slowly, stirring often, until they become golden brown and caramelized, about 20-25 minutes. This step might test your patience, but that deep, sweet onion flavor is worth every minute.
4. Add the minced garlic to the onions and cook for another 1-2 minutes until fragrant.
5. Transfer the caramelized onions and garlic into the slow cooker. Place the seared roast on top.
6. Pour in beef broth, white wine (if using), and Worcestershire sauce. Sprinkle thyme over everything.
7. Cover and cook on LOW for 8-9 hours, or on HIGH for 4-5 hours, until the meat is fork-tender and falling apart.
8. Once the roast is done, carefully remove it from the slow cooker and set it aside to rest.
9. To thicken the sauce, mix the flour with a few tablespoons of cold water to make a slurry. Stir the slurry into the slow cooker juices. Turn the slow cooker to HIGH and cook uncovered for 10-15 minutes until the sauce thickens. Stir occasionally.
10. Slice or shred the roast, spoon the rich onion gravy over the top, and serve.

One little secret I learned from Mama Lu’s kitchen is that letting the meat rest before slicing helps keep every bite juicy and tender — a small step that makes a big difference.