Pat the steak cubes dry with paper towels and season well with salt and pepper.
Heat olive oil in a large skillet over medium-high heat until shimmering.
Add the steak cubes in a single layer. Sear on each side for about 2 minutes, until golden brown.
Reduce the heat to medium. Add butter and garlic to the skillet, stirring quickly so the garlic doesn’t burn.
Toss the steak bites in the garlic butter until coated and fragrant.
Sprinkle with parsley and parmesan before serving, if desired.