Before preparing any other ingredients, place the steak in the freezer for 30-40 minutes until firm. This will make it easier to slice thinly without a deli slicer or specialist equipment.
Add a splash of olive oil to a heavy-based pan and heat until shimmering. Add the sliced peppers to the pan and decrease the heat to medium-low. Cover the pan and stir occasionally, cooking for 10-15 minutes until the peppers are soft. If the peppers brown too quickly add a splash of water.
Once soft, remove the lid and increase the heat to medium-high. Cook for another 5-10 minutes until the peppers are lightly caramelised, adding a generous pinch of salt and an optional tablespoon of white sugar 1-2 minutes before the end of the cooking time.
Remove the beef from the freezer and cut into very thin slices. Divide the meat into roughly 250g portions, using sheets of greaseproof paper or cling film as dividers.
Slice bread in half lengthwise, keeping a long side intact, then heat a large griddle over high heat. (If you don’t have a griddle, use a large saucepan – ideally cast-iron – and cook one portion of meat at a time).
Add a small drizzle of oil to each portion of sliced steak then place two portions onto the griddle (or one onto a frying pan) and reduce the heat to medium-high. Season generously with salt and black pepper, then use two metal spatulas or large spoons/forks to press and pull slices apart, ultimately tenderising the meat even further. After 2 minutes of cooking, flip the steak over then top with a large scoop of the peppers, then top with enough slices of provolone to cover each pile of meat (approx. 4 slices). Reduce the heat to medium and cook, without turning, until the meat is browned underneath and the cheese has melted slightly. This should take between 2-4 minutes.
Once the cheese has melted, transfer each portion to a submarine roll. Quickly wrap with a layer of greaseproof paper, then foil. Leave to rest for at least five minutes before eating.