1. Cook the Pasta Shells:
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Bring a large pot of generously salted water to a boil.
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Add the jumbo shells and cook according to package directions for al dente (usually 9-11 minutes). They should still have a slight bite so they don’t tear when stuffing.
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Drain carefully and rinse with cool water to stop the cooking process. Drizzle with a little olive oil to prevent sticking and set aside.
2. Prepare the Filling:
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While the pasta cooks, heat the olive oil in a large skillet over medium-high heat.
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Add the thinly sliced steak, seasoning with salt and pepper. Cook until just browned, breaking it up as it cooks (about 3-5 minutes). Remove the steak with a slotted spoon to a large bowl, leaving the drippings in the pan.
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In the same skillet, add the diced onion, bell pepper, and mushrooms (if using). Sauté for 6-8 minutes, until the vegetables are soft and lightly browned.
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Add the minced garlic and cook for one more minute until fragrant. Stir in the Worcestershire sauce.
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Return the cooked steak to the skillet, stir everything to combine, and remove from heat. Let the mixture cool slightly.
3. Make the Cheese Sauce:
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Whisk in the flour and cook for 1-2 minutes to form a smooth paste (a roux).
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Gradually pour in the milk, whisking constantly to prevent lumps.
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Continue to cook, whisking frequently, until the sauce thickens enough to coat the back of a spoon (about 5-7 minutes).
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Remove from heat and whisk in 1 cup of shredded provolone cheese until melted and smooth. Season with a pinch of nutmeg, salt, and white pepper.
4. Assemble the Dish:
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Preheat your oven to 350°F (175°C). Lightly grease a 9×13 inch baking dish.
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Pour about ½ cup of the cheese sauce into the bottom of the baking dish and spread it into a thin, even layer.
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To the slightly cooled steak and veggie mixture, add ½ cup of the remaining shredded provolone cheese and ½ cup of the cheese sauce. Mix well. This is your filling.
5. Bake:
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Pour the remaining cheese sauce evenly over the top of the stuffed shells.
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Sprinkle the top with the shredded mozzarella and grated Parmesan cheeses.
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Cover the dish with foil and bake for 20 minutes.
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Remove the foil and bake for an additional 10-15 minutes, or until the cheese is golden and bubbly.
6. Serve:
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Let the shells rest for 5-10 minutes before serving. This allows the cheese sauce to set slightly.
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Garnish with chopped fresh parsley if desired.
Chef’s Notes & Tips:
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Shaving the Steak: For super thin slices, partially freeze the steak for 30-60 minutes. It will be much easier to slice thinly against the grain.
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Shortcut: Look for pre-shaved steak (sometimes labeled “beef for cheesesteak”) in your grocery store’s meat section or freezer aisle.
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Cheese Variations: Feel free to use Cheez Whiz in the sauce for an ultra-authentic Philly experience, or substitute with sharp white cheddar.
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Make Ahead: You can assemble the entire dish, cover, and refrigerate it up to 24 hours in advance. Let it sit at room temperature for 20-30 minutes before baking. You may need to add 5-10 minutes to the baking time if it goes in cold.
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Freezing: Assemble the unbaked dish, wrap tightly in plastic wrap and foil, and freeze for up to 2 months. Thaw in the refrigerator overnight before baking as directed.
Enjoy your delicious, cheesy creation