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

Pat steak cubes very dry and season generously with salt and black pepper.

Heat a large skillet over medium heat. Add 2 tablespoons butter and 1 tablespoon olive oil. When butter foams, stir in minced garlic and cook 45–60 seconds until fragrant (do not brown).

Increase heat to medium-high, add remaining olive oil if needed, and sear steak in a single layer 2–3 minutes per side until browned and medium-rare to medium. Transfer steak to a plate to rest; keep pan on heat.

Lower heat to medium-low. Pour in beef broth and scrape up browned bits. Add heavy cream and remaining 2 tablespoons butter; stir to combine and bring to a gentle simmer (do not boil).

Gradually add mozzarella and fontina, whisking until melted and smooth. Whisk in parmesan, then gorgonzola if using. Season sauce with pepper and a pinch of salt to taste.

Add drained rigatoni to the skillet and toss to coat. If sauce is too thick, loosen with splashes of reserved pasta water until glossy and silky.

Return steak (and any resting juices) to the skillet and toss gently over low heat 1–2 minutes to warm through without overcooking.

Garnish with chopped parsley and serve hot with extra parmesan if desired.