1. Prepare the Crust:

1. Season the chuck roast all over with salt and pepper. Heat olive oil in a large skillet over medium-high heat and sear the roast on all sides until browned, about 4-5 minutes per side. Transfer the roast to a slow cooker.
2. In the same skillet, add the onion and cook for 3-4 minutes until softened. Add the garlic and mushrooms and cook for another 5 minutes until the mushrooms release their liquid. Pour in 1/2 cup of the beef broth to deglaze the pan, scraping up any browned bits. Transfer the entire mixture to the slow cooker.
3. Add the remaining beef broth, Worcestershire sauce, and dried thyme to the slow cooker. Cover and cook on low for 8 hours or on high for 4-5 hours, until the beef is fork-tender.
4. Remove the beef from the slow cooker and shred it with two forks. In a small bowl, whisk together the sour cream and flour until smooth. Slowly whisk about 1 cup of the hot liquid from the slow cooker into the sour cream mixture to temper it. Then, pour this mixture back into the slow cooker and stir to combine.
5. Return the shredded beef to the slow cooker and stir to coat in the sauce. Cook on high for an additional 15-20 minutes until the sauce has thickened. Serve immediately over cooked egg noodles, garnished with fresh parsley.