Cook the fettuccine or spaghetti according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.

In a large skillet over medium-high heat, melt 2 tablespoons of butter. Season the steak strips with salt and pepper, then add them to the skillet. Cook for about 3-4 minutes until browned and cooked to your desired doneness. Remove the steak from the skillet and set aside.

In the same skillet, add the remaining 2 tablespoons of butter and minced garlic. Sauté for about 1 minute until fragrant, being careful not to burn the garlic.

Add the cooked noodles to the skillet along with the soy sauce, Worcestershire sauce, and red pepper flakes (if using). Toss to combine, adding reserved pasta water a little at a time to create a sauce.

Return the cooked steak to the skillet and toss everything together until well mixed and heated through. Adjust seasoning with salt and pepper if needed.

Serve immediately, garnished with sliced green onions and chopped parsley.