Grill steaks seasoned with salt and freshly ground black pepper to your preference. Let rest. Prepare Steak Diana Sauce below.
Steak Diana Sauce: In a small skillet melt butter over medium heat. Sauté mushrooms, green onions and parsley. Add lemon juice, Worcestershire sauce, dry mustard and salt, sauté about 10 minutes. Plate the steaks and smother with the sauce. Enjoy!