Season the beef chuck roast generously with salt and pepper.

In a large skillet, heat the olive oil over medium-high heat. Sear the roast on all sides until browned, about 3-4 minutes per side.

Transfer the seared beef to a slow cooker. Add the sliced onion, beef broth, and Worcestershire sauce. Cover and cook on low for 8 hours or on high for 4 hours until the meat is fork-tender.

Once cooked, remove the beef from the slow cooker and let it rest for a few minutes. Shred the beef using two forks. Strain the broth and set aside for dipping.

Preheat your oven to 350°F (175°C). Split the French rolls or baguettes and layer in the shredded beef and a slice of provolone cheese.

Place the sandwiches on a baking sheet and bake for about 10 minutes, or until the cheese is melted and bubbly.

Serve hot with the reserved broth in small bowls for dipping. Garnish with fresh parsley if desired.