Heat a large skillet over medium-high heat until hot. Melt half of the butter in the skillet, then add the seasoned steak pieces. Sear each side for 2-3 minutes until a golden-brown crust forms. Transfer the steak to a plate and set it aside.

In the same skillet, lower the heat to medium and add the remaining butter. Once melted, stir in the minced garlic and crushed red pepper flakes, sautéing for about 1-2 minutes until fragrant.

Pour in the heavy cream, stirring to combine with the garlic mixture. Allow the sauce to simmer for 3-4 minutes until it slightly thickens. Mix in the grated Parmesan cheese if using.

Add the dry rotini to the skillet along with enough water or broth to cover the pasta completely. Cook for 10-12 minutes until the pasta is al dente and has absorbed the creamy sauce.

Return the reserved steak to the skillet, tossing it gently with the pasta and sauce. Adjust seasoning with salt and pepper to taste.

Serve immediately, garnished with freshly chopped parsley and extra Parmesan if desired.