Pat the chuck roast completely dry with paper towels. Season generously on all sides with salt and pepper.
3 pounds chuck roast, fine sea salt, fresh ground black pepper
Heat the avocado oil in your Dutch oven over medium-high heat.
2 tablespoons avocado oil
Place the roast in the hot pot and sear for 4-5 minutes per side, until browned all over. Remove from the pot and set aside on a plate.
Reduce the heat to medium-low. Add the butter to the Dutch oven. Once melted, add the onions.
2 tablespoons unsalted butter, 3 large yellow onions
Cook slowly, stirring occasionally, until the onions are caramelized and soft. This takes patience – allow at least 30-45 minutes.
Add the minced garlic during the last 30 seconds of cooking the onions, stirring until fragrant.
4 cloves garlic
Increase the heat to medium-high. Pour in the beef broth, Worcestershire sauce, bay leaves, dried thyme and dried oregano. Bring the mixture to a simmer. Taste and add salt and pepper as needed.
3 cups beef broth, 2 tablespoons Worcestershire sauce, 2 bay leaves, 2 teaspoons dried thyme, 1 teaspoon dried oregano
Return the chuck roast and any accumulated juices from the plate to the pot with the simmering liquid. Bring the liquid back to a gentle simmer on the stovetop.
Reduce heat to low, cover with a tight-fitting lid, and simmer gently on the stovetop or in a 300°F oven for 3½ to 4 hours, or until the beef is fork-tender. Check occasionally to make sure the liquid is just simmering gently and not boiling; add a bit of water or broth if necessary to maintain liquid level.
When the beef is tender, carefully remove the roast from the pot to a large plate or bowl. Remove and discard the bay leaves.
In a small bowl, whisk together cornstarch and water to make a slurry. Slowly whisk the slurry into the liquid. Continue to cook and whisk for 1-2 minutes until the sauce thickens.
2 tablespoons cornstarch, 4 tablespoons water
Return the roast to the pot with the thickened sauce. Use two forks to shred the beef directly in the pot, mixing gently to combine the meat evenly with the sauce.