Mix the rub: Combine all 11 rub ingredients in a bowl and mix well. This makes enough for 4 steaks and the leftover keeps in a sealed jar.
Rub the steaks: Generously press the spice mixture into both sides of each steak. Season with extra salt and pepper. Leave at room temperature for 15-20 minutes.
Make the herb butter: Mash the softened butter with the chopped chives and parsley. Set aside.
Preheat: Set the air fryer to 200C (390F).
Cook: Place the steak in the air fryer basket. Cook for 10 minutes, flip, and cook for another 10 minutes for medium-rare.
Rest and serve: Transfer to a board, top with a knob of herb butter and rest for 5 minutes. Slice at an angle against the grain.
