Slice partially frozen steak in thin pieces, cutting against the grain. Season with the salt and pepper and set aside.
Prepare the onions, peppers, mushrooms and garlic by slicing / mincing according to ingredient lit. Set aside.
In a large skillet, heat half of the butter (or oil) to high heat. When the skillet is very hot, cook the seasoned steak pieces in small batches. You want them to brown quickly but not burn. Move the pieces to cook on all sides for about 2 minutes. Transfer to a covered dish.
Once the steak is cooked, add the remaining butter or oil to the skillet. Add the sliced onions, peppers, mushroom, and garlic. Let them brown for 1 - 2 minutes, then reduce the heat to medium low. Sprinkle with salt and pepper to taste. Cook for about 10-15 minutes until the vegetables are tender, stirring occasionally to prevent sticking.
Add the cooked steak back to the skillet with the vegetables. Stir in the Worcestershire sauce and soy sauce. Turn skillet off but keep warm.
Serve on toasted bakery buns with a generous portion of cheddar cheese.
This recipe will make 4 large sandwiches. If you use smaller rolls, it will make 6 - 8.