Heat olive oil in a large skillet over high heat.
Add steak pieces and season with salt and pepper.
Sear the steak for 2 minutes without stirring to develop a crust.
Stir and cook for another 2 minutes until golden brown. Cook in batches if needed.
Remove steak from skillet and set aside.
Reduce heat to medium and melt butter in the same skillet.
Add garlic and red pepper flakes; cook for 30 seconds until fragrant.
Return steak to skillet and toss in the garlic butter sauce.
Garnish with parsley and serve immediately.