Step 1: Preheat your oven to 350 °F (175 °C). Lightly grease a 9×5″ (23×13 cm) loaf pan or line it with parchment paper for easy removal.
Step 2: In a small bowl, combine 1 cup breadcrumbs with ½ cup milk. Let rest for 3–5 minutes, until the milk is fully absorbed and the mixture is moistened.
Step 3: Meanwhile, heat 1 Tbsp olive oil in a skillet over medium heat. Add the finely chopped onion, bell pepper, and minced garlic, and sauté for about 4 minutes, until the vegetables soften. Remove from heat and allow to cool slightly.
Step 4: In a large bowl, combine the 2 lbs ground beef, the soaked breadcrumb mixture, 1 large beaten egg, 2 Tbsp Worcestershire sauce, 1 tsp salt, and ½ tsp pepper. Add the cooled sautéed vegetables, then gently mix with your hands or a sturdy spoon until just combined. Avoid overmixing.
Step 5: Transfer the meat mixture into the prepared loaf pan. Press down evenly and smooth the top with a spatula.
Step 6: Place the prepared loaf pan in your preheated 350 °F (175 °C) oven. Bake for 45 minutes.
Step 7: While the meatloaf bakes, heat a clean skillet over medium–high heat. Add the thinly sliced beef, seasoning lightly with salt and pepper. Sear, stirring constantly, until just browned (about 3–4 minutes). Transfer to a plate and cover.
Step 8: In the same skillet, add a drizzle of olive oil if needed, then the thinly sliced onion and bell pepper. Sauté over medium heat for 3 minutes, or until tender-crisp. Remove from heat.
Step 9: After the initial 45-minute bake, remove the meatloaf from the oven. Arrange the cooked steak slices, then the sautéed onions and peppers, and finally, the 6 slices of provolone cheese over the loaf.
Step 10: Return to the oven for an additional 5–7 minutes, or until the provolone is fully melted and bubbling. You can broil for 1-2 minutes for a golden top.
Step 11: Remove from the oven and let rest in the pan for 10 minutes. Lift out and slice into 8 even pieces.
Step 12: Serve on toasted hoagie rolls or atop mashed potatoes. Garnish with chopped fresh parsley.