Heat a large skillet over high heat.
Add the olive oil and allow it to heat until hot.
Add the bite-sized sirloin steak pieces to the skillet in a single layer.
Season the steak with salt and black pepper to taste.
Sear the steak pieces on all sides until well browned.
Cook only until the steak reaches the desired level of doneness. Since the steak is cut into small pieces, only a few minutes of cooking time are needed.
Reduce the heat slightly, if necessary.
Add the unsalted butter and minced garlic to the skillet.
Stir gently until the butter is melted and the garlic is fragrant.
Toss the steak bites in the garlic butter until evenly coated.
Remove the skillet from the heat.
Garnish with freshly chopped parsley.
Serve immediately while warm.