Start by cutting the sirloin into bite-sized cubes, making sure they’re as even as possible so they cook evenly. Pat them dry with paper towels and season with salt and pepper. Drying helps get that beautiful sear later.
Heat olive oil in your skillet over high heat until it’s hot and shimmering. Add the steak cubes in a single layer—avoid overcrowding. Cook the cubes for 3–4 minutes until golden brown on at least one side, stirring occasionally for even colour. Work in batches if necessary.
Once the steak is seared, reduce the heat slightly and add butter and minced garlic to the pan. Stir quickly to coat all the steak pieces in the hot garlic butter for 1–2 minutes. Be careful not to burn the garlic—it should be fragrant, not brown. Sprinkle with parsley and serve right away for the best flavour.