Let the steak come to room temperature, prepare salted boiling water for pasta, mince garlic, chop parsley, and measure remaining ingredients.
Cook pasta according to package directions until al dente, reserve 1 cup pasta water, then drain and set aside.
Heat skillet over medium-high heat until very hot, season steak with salt and pepper, add 1 tablespoon butter, and sear steak 3-4 minutes per side for medium-rare, then remove and rest.
Reduce heat to medium, add remaining butter, cook garlic 30 seconds until fragrant, then stir in Worcestershire sauce and beef broth scraping browned bits and simmer for 2 minutes.
Add heavy cream, bring to a gentle simmer, then stir in parsley, salt, pepper, and red pepper flakes if using, cooking 2-3 minutes until slightly thickened. Adjust sauce with reserved pasta water if needed.
Slice rested steak against the grain into bite-sized pieces, add pasta and steak to skillet, toss gently to coat with sauce, and adjust consistency with more pasta water if necessary.
Serve immediately garnished with extra parsley, freshly cracked black pepper, and optional fresh Parmesan.