Heat a large skillet over medium heat. Add the vegetable oil and butter. Add the bell pepper and onion and cook, stirring often until softened and golden brown, about 30 minutes Add the Worcestershire sauce and mix well. Cook for a few minutes until the liquid is reduced and transfer to a bowl to cool.

To a large mixing bowl add the ground beef. Add the cooled peppers, onions, Worcestershire sauce, ground pepper. Mix well and portion into 4 patties about 1/2 inch thick. Make them thicker at the edges.

Salt the patties after they are formed and let sit for 10 minutes before cooking.

Heat a cast iron skillet over medium high heat until it just starts to smoke. Cook the patty for 4 minutes for medium well and turn once.

Cook for 3 minutes. *see note

If you are adding cheese, add the sliced cheese now and tent with foil so the cheese melts. Cook for a further 1 minute until the cheese is melted. Remove from the pan and allow to rest.

Serve on your favorite bun with your favorite toppings.