Cut the steak into bite-sized cubes, about ¾ inches. Season the cubes with salt and pepper.
1 ½ pounds sirloin steak, ½ teaspoon kosher salt, ½ teaspoon coarse ground black pepper
Heat a large heavy-bottomed skillet over medium-high heat. When hot, add oil and swirl pan to coat bottom of pan with oil.
1 tablespoon olive oil
Add steak bites in an even single layer to the hot skillet (see note). Cook without stirring for 3 minutes. Stir and continue to cook for 3 to 4 minutes, stirring occasionally, or until the steak bites reach desired level of doneness. For medium-rare, cook them until they are browned on the outside but still slightly pink in the center (internal temperature of 130 to 135°F). Adjust the cooking time based on your preference.
Transfer steak bites to a plate and tent with foil to keep warm. (The internal temperature will continue to rise a few degrees.)
Return pan to stove and reduce heat to medium-low. Add butter, garlic, and rosemary. Heat until butter is melted and garlic is fragrant, 1 to 2 minutes.
Turn off heat, return steak to pan, and toss to coat in garlic butter. Taste and season with additional salt and pepper, if desired. Sprinkle with parsley and serve immediately.
2 tablespoons minced fresh parsley
Video
Notes
Cooking tip: The skillet should be hot before adding the steak. Don't overcrowd the pan. There should be a little space between the cubes of beef. If necessary, sear the steak in batches, adding oil as needed.
Serving suggestions: Serve the garlic butter steak bites hot as an appetizer or main dish. They pair well with a side of vegetables and/or potatoes.