Brown the Chuck Roast: This step is optional, but it does add a lot of flavor. Season the beef with salt and pepper. Heat olive oil in a large skillet over medium-high heat. Add the chuck roast roast pieces and sear on all sides until browned, about 2-3 minutes per side. This step locks in flavor but can be skipped if you're short on time. Transfer the browned meat to the crockpot.
Assemble the "Pie": Add the carrots, onion, garlic, corn, and mushrooms to the crockpot. Then add the tomato paste, Worcestershire Sauce, beef broth, brown gravy mix, and Italian Seasoning. Stir until everything is mixed together.
Slow Cook: Cover and cook on LOW for 7-8 hours or on HIGH for 4-5 hours, until the chuck roast is tender.
Add the Peas and Potatoes: Once the beef is fully cooked, stir in the frozen peas to the "pie" filling. Spread the premade mashed potatoes evenly on top of the beef and vegetable mixture. If you like, sprinkle shredded cheese over the mashed potatoes for extra richness.
Final Touches: Cover and cook on HIGH for an additional 30 minutes, or until the mashed potatoes are heated through and the cheese is melted. Garnish with fresh parsley before serving for a pop of color.
