Boil fettuccine in salted water until al dente; reserve 0.5 cup pasta water and drain.
Season steak strips with salt and pepper.
Heat olive oil in a large skillet over medium-high heat; sear steak strips for 2 minutes per side until browned. Remove steak from skillet.
Reduce heat to medium and melt butter in the same skillet; sauté garlic for 1 minute.
Pour in heavy cream and bring to a light simmer.
Gradually whisk in Parmesan cheese until fully incorporated and the sauce thickens.
Incorporate the steak and pasta into the sauce, adding reserved pasta water if needed for consistency.
Garnish with parsley and serve immediately.