Preheat the air fryer to 400°.
Cut steak into 1-inch pieces.
Cut the mushrooms into quarters.
Microwave butter and one tbsp of steak sauce until butter is melted.
Toss steak with 1 tbsp of the melted butter steak sauce and refrigerate for 1 hour.
Preheat Air Fryer to 400°.
Place the steak and mushrooms into a large bowl and toss with salt and pepper.
Cook in the air fryer for 5 minutes.
Garnish with fresh parsley.
Serve with remaining butter/steak sauce. (Warm the sauce in the microwave if desired.)