Preheat your oven to 350 degrees.Season the beef chuck roast generously with salt and pepper on all sides. Heat the avocado oil in a large oven-safe pot or Dutch oven over medium-high heat. Once the oil is hot, add the roast and sear it on all sides until browned. This will help to develop rich flavors. Remove the seared roast from the pot and set it aside. In the same pot, add the sliced onion and sauté until they are softened and fragrant.
Add the beef broth, whiskey, tomato paste, and dried thyme to the pot. Stir well to combine the ingredients. Return the seared roast to the pot, along with any accumulated juices. Cover the pot with a lid and transfer it to the preheated oven. Roast the pot roast for about 2-3 hours, or until the meat is tender and easily pulls apart with a fork. Check the roast occasionally and bake it with the cooking liquid. Once the roast is tender, remove it from the oven and transfer it to a cutting board. Let it rest.
While the roast is resting, add the carrot chunks and cabbage wedges to the pot with the cooking liquid. Return the pot to the oven and roast for an additional 20-30 minutes, or until the vegetables are tender. Slice the pot roast against the grain into medium- thick slices. Serve the slices of pot roast with the roasted cabbage and carrots, along with some of the flavorful cooking liquid.
