Heat half of the olive oil in a large skillet over high heat.Add the thinly sliced steak, salt, black pepper, and paprika.
Sauté for 5–6 minutes, stirring occasionally, until the beef is browned and cooked through. Transfer the steak to a bowl and set aside.Tip: Do not overcook the steak—it should stay tender and juicy.
Cook the Vegetables
Reduce the heat to medium and add the remaining olive oil to the same skillet.
Add the onions, mushrooms, and bell peppers. Sauté for about 5 minutes, or until softened and slightly caramelized.
Transfer the cooked vegetables to the bowl with the steak.
Add the Cheese
While everything is still warm, add the cream cheese and shredded mozzarella to the bowl. Mix well until fully combined and the cheese melts.
Assemble the sandwich
Slice the sandwich rolls lengthwise and fill each roll generously with the steak and vegetable mixture. Serve immediately while hot and melty.
Notes
Use soft rolls, not crusty ones—they absorb the juices and taste better.