Start by boiling the pasta in a large pot of salted water. Cook it just until al dente—it’ll finish cooking in the sauce later. Before draining, scoop out about a cup of pasta water and set it aside. The starch in this water helps bind the sauce beautifully to the pasta.
Heat olive oil in a large skillet over high heat. Add the steak slices, season with half the salt and pepper, and cook for 3–4 minutes until browned but still tender. Remove the steak from the pan and set it aside—you’ll add it back later.
In the same pan, melt the butter over medium heat. Toss in the onion and bell peppers, and cook for about 4 minutes, stirring occasionally. When they start to soften, add the minced garlic and cook for another 30 seconds, just until fragrant.
Reduce the heat to medium-low. Pour in the heavy cream and Worcestershire sauce, stirring to deglaze the pan and lift up all those flavorful brown bits. Let the sauce simmer gently for 2–3 minutes until slightly thickened.
Return the cooked steak to the skillet along with any juices. Add the drained pasta and toss to coat everything in the sauce. Sprinkle in the mozzarella cheese and stir until it melts into a creamy, luscious coating. If the sauce feels too thick, splash in a bit of the reserved pasta water until it reaches your desired consistency.
Once everything’s coated and creamy, remove from heat. Taste and adjust seasoning if needed. Serve immediately while the sauce is silky and the cheese is melty—you want it hot and fresh!