Bring a large pot of salted water to a boil. Cook the shell pasta according to package directions until al dente. Before draining, reserve about 1 cup of the starchy pasta water.

While the pasta cooks, pat the steak dry and cut it into 1-inch cubes. Season with salt and pepper. Heat olive oil in a large skillet over medium-high heat. Add steak in a single layer and sear for 1-2 minutes per side until a brown crust forms. Remove steak and set aside.

Reduce heat to medium, add butter to the skillet. Once melted, add minced garlic and cook for 30 seconds until fragrant.

Pour in beef broth to deglaze, scraping up browned bits. Simmer for 2-3 minutes. Stir in the heavy cream and bring to a gentle simmer.

Stir in the grated Parmesan cheese until smooth. Return the seared steak bites to the skillet. Add the drained pasta and toss to coat. If needed, thin the sauce with a splash of reserved pasta water.

Garnish with fresh parsley and serve immediately.