Season the chuck roast with 1 teaspoon kosher salt and 1/4 teaspoon black pepper.
Place the roast in the slow cooker pan and add the sliced onion, garlic and parsley. Pour the beef broth (or wine) on top.
Cover and cook on low for 7 hours.
Remove the slow cooker pot roast to a plate. Set the slow cooker to WARM. Strain the cooking juices into a glass measuring cup, then return the beef to the slow cooker and cover, to keep warm while you make the gravy.
Use a spoon to skim the fat layer off the top of the cooking juices. Season with 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Transfer to a medium saucepan. Heat over medium heat, and continue to simmer, whisking occasionally, until reduced into a rich sauce, about 10 minutes.
Flake the beef with a fork. Distribute evenly among plates lined with mashed cauliflower. Spoon 2-4 tablespoons of gravy on top of each plate and serve.
Nutrition info is from Fitday.com and based on a search for "Beef, chuck, arm pot roast, separable lean and fat, trimmed to 1/8" fat, choice, cooked, braised."