In a skillet over medium heat, cook the ground beef with the diced onion until browned, then transfer to the slow cooker. Add the potatoes.

In a bowl, combine salt, black pepper, garlic powder, French onion soup, French onion soup mix, and beef broth, then pour over the beef and potatoes and stir to combine.

Cover and cook on LOW for 4–5 hours until the potatoes are tender. In a small bowl, whisk together the cornstarch and water, then stir it into the slow cooker.

Cover and cook for an additional 10–15 minutes until the sauce thickens into a rich gravy. Stir gently, top with provolone cheese and allow it to melt, then finish with parsley before serving.