Bring a large pot of salted water to a boil. Cook shell pasta until al dente per package instructions. Reserve 1/2 cup of pasta water, then drain and set aside.

Pat steak bites completely dry with paper towels. Season generously with salt and black pepper.

Heat olive oil in a large skillet over medium-high heat. Sear steak bites in a single layer for 2-3 minutes per side until deeply browned. Work in batches if needed. Transfer to a plate and loosely tent with foil.

Reduce skillet heat to medium. Add butter and minced garlic. Saute for about 1 minute until fragrant — do not let the garlic brown.

Pour in heavy cream and bring to a gentle simmer. Gradually whisk in Parmesan cheese until smooth and velvety. Season with salt and pepper. Stir in pasta water as needed to reach desired consistency.

Add cooked shell pasta to the sauce and toss gently to coat. Simmer together for 1-2 minutes.

Divide pasta among bowls. Top with warm steak bites and any plate juices. Garnish with fresh parsley if using. Serve immediately.