Prepare the raw beef by cutting it into inch-long slabs of meat.
Heat up your skillet on your grill to a medium heat. Add oil.
Transfer the beef to the skillet and allow it to brown.
Add the Worcestershire sauce, salt and pepper to the pan. Cook for a further minute or two.
Remove beef from pan and sit to one side.
In the same pan add butter, chopped onion, and peppers. Caramelize until the onion starts to brown.
Add the meat back to the mix and combine well over heat.
Prepare toasted bread by buttering each side. Add meat mixture straight from the pan.
Top with cheese and leave for a minute to allow it to melt. Serve and enjoy.