Season the steak. Rub about 1/2 tablespoon olive oil on the steak. Season it with salt and pepper on all sides, and set it aside.
Boil the pasta. Cook the pasta according to package instructions. Drain it and set it aside.
Cook the garlic and shallot. Meanwhile, melt the butter in a large skillet set over medium heat. Add the garlic and shallot. Let them cook for 2 minutes, and stir frequently.
Make the sauce. To the skillet, add the heavy cream and milk. Then, whisk in the cream cheese and parmesan. Whisk the sauce for 5 minutes or until the cheese has melted and the sauce is smooth and creamy. The sauce should thicken slightly. Season with salt and pepper to taste. Let it simmer for 5 minutes.
Combine the pasta and sauce. Reduce the heat to low and gently stir the fusilli into the sauce until it's completely coated. Let it cook for 2 to 3 minutes or until warm. Remove it from the heat and set aside.
Cook the steak. Add the remaining olive oil to a cast iron skillet (or to the same skillet you used for the sauce) and set over medium-high heat. Add the ribeye and let it cook for 4 to 6 minutes on each side or until done to taste. The internal temperature should read 130˚F to 135˚F for a medium-rare steak.
Let it rest. Remove the steak from the heat and transfer it to a plate. Let it rest for 5 minutes, then cut it into 1-inch thick slices.
Finish and serve. Taste the pasta and adjust the seasoning with more salt and pepper if needed. Serve the pasta topped with slices of steak, chopped parsley, and parmesan cheese.
Notes
Steak: Ribeye is a favorite around here, especially with pasta, but you can also use top sirloin. Cook the steak to a desired doneness, but I suggest not cooking it over 135˚F.
Fusilli: Pasta with corkscrew shapes tends to hold onto sauce better than other shapes; however, you can use any pasta you prefer. Also, no-carb noodles, zoodles, or whole-wheat pasta are great options.
Cream Sauce: If you want to use Half & Half instead of Heavy Cream, you can definitely do so. I also suggest continuously whisking the sauce until creamy and smooth.