Cook pasta shells in salted boiling water until al dente. Drain and reserve some pasta water.

Season steak with salt and pepper. Sear in hot skillet with olive oil for 1–2 minutes per side. Remove and set aside.

In same skillet, melt butter and sauté onion and garlic until soft and fragrant.

Add beef broth to deglaze pan, then stir in cream and simmer until slightly thickened.

Stir in Parmesan until smooth, then add pasta shells and toss to coat.

Return steak to skillet and simmer briefly until heated through. Serve hot.