Meanwhile, slice your steak into bites, ensuring the marbling of fat is evenly distributed with each piece (you want to avoid having a whole piece made out of fat!).
Add to a bowl with the cornflour and seasoning. Toss to combine, then add the oil, salt and pepper. Stir again until well incorporated.
Using tongs, add the steak bites to the preheated air fryer basket. Cook at 400°F (200°C) for 2 minutes for medium rare, 3 minutes for medium rare or 5 minutes for minutes for well-done.
During this time, melt the butter in the microwave for 30-45 seconds. Squish the garlic into a paste with a pinch of salt, then add to the melted butter, along with the parsley. Stir to combine and season with salt.
Serve your steak bites with a drizzle of garlic butter, or use it as a dip. Enjoy!