Pat the steak bites thoroughly dry with paper towels. This is crucial for a good sear. In a medium bowl, toss the steak cubes with olive oil, salt, and black pepper until evenly coated.

Heat a large cast-iron skillet or heavy-bottomed pan over medium-high heat until it just begins to smoke. Add the seasoned steak bites in a single layer, ensuring not to overcrowd the pan. Cook in batches if necessary.

Sear the steak for 1-2 minutes per side, turning with tongs, until a deep brown crust forms and the steak reaches your desired doneness (medium-rare to medium is recommended for tender bites). Remove the cooked steak bites from the skillet and set aside on a plate.

Reduce heat to medium-low. Add the butter to the same skillet and let it melt. Once melted, add the minced garlic and red pepper flakes (if using). Sauté for about 30-60 seconds until fragrant, being careful not to burn the garlic.

Return the seared steak bites to the skillet with the garlic butter. Toss gently to coat all the steak pieces in the flavorful sauce. Stir in the fresh chopped parsley.

Serve hot immediately as a main course with sides like mashed potatoes or roasted vegetables, or as an appetizer with toothpicks.