To begin, prepare the green beans. Bring a pot of salted water to a boil, add the green beans, and cook until tender but still vibrant green, about 5-7 minutes. Immediately transfer them to a bowl of ice water to stop cooking and preserve their colour. Drain and set aside.

Slice the tomatoes into thin rounds and set them aside on a plate. If using ají verde, finely chop it and mix it with the mayonnaise for a mild kick. Cover and refrigerate the mayonnaise mixture until needed.

Season the steak slices generously with salt and freshly ground black pepper on both sides. Heat the vegetable oil in a large skillet over medium high heat.

Cook the steak in the skillet, working in batches if necessary to avoid overcrowding. Sear each side for about 2-3 minutes until browned and cooked to your desired doneness. For the most authentic flavour, aim for medium rare to medium. Remove the steak from the skillet and let it rest on a plate covered with foil.

While the steak rests, lightly toast the sandwich rolls. Slice them in half horizontally and place them in a preheated oven at 180°C (350°F) for 3-5 minutes, or toast them on a griddle for a crispier texture.

Spread a generous layer of the ají mayonnaise mixture (or plain mayonnaise if preferred) on the bottom half of each toasted roll.

Assemble the sandwiches. Layer the steak slices evenly on the bottom half of the rolls, followed by a generous handful of cooked green beans. Add slices of tomato on top and optional lettuce for extra crunch.

Close the sandwiches with the top half of the rolls. Serve immediately, accompanied by a side of fries or a fresh salad. To enhance the experience, consider pairing with a chilled glass of Chilean beer or a fruity soda. For presentation, slice the sandwich diagonally and secure with a toothpick if needed.