In a large frying pan over high heat, add olive oil and heat so that a drop of water will sizzle when you drop it in the oil; lower heat to medium. Add onions and mushrooms, stir and cook until mushrooms darken and onions start to look transparent. Add steak slices and cook for 3 minutes or until meat lightly browns. Add salt and pepper to taste.

Heap cooked meat mixture in a long pile across pan, Lay cheese slices over meat until melted. If using Cheese Whiz, melt in a double boiler or in the microwave.

Slice bread lengthwise. Using a spatula, scoop meat mixture and cheese and lay on bread with cheese on top. If using melted Cheese Whiz, ladle it on top. slice sandwich into 2 or 4 pieces, and serve with a dill pickle.

Makes 2 servings.