Shaved Steak Sandwiches with Onions and Cheese

Brown the onions. Heat 15 ml of the oil in the frying pan over medium-high heat until shimmering. Add the onions and ¼ tsp of the salt and cook, stirring often, until soft and well browned, 6-12 min. Spoon into a bowl.

Sear the first batch. Heat another 15 ml oil in the empty pan over high heat until it just begins to smoke. Spread half the steak in an even layer and leave it undisturbed for about 5 min, until well browned underneath. Stir and cook for about 2 min more, until no pink remains. Transfer to a colander set over a large bowl.

Repeat and drain. Wipe the pan clean with paper towels. Heat the remaining 15 ml oil over high heat until just smoking and cook the remaining steak the same way: about 5 min without stirring, then about 2 min while stirring, until no pink remains. Add to the colander, let the excess juices drain away and discard the liquid collected in the bowl.

Reheat the filling. Return all the drained steak to the empty pan with the onions, remaining ½ tsp salt and pepper. Cook over medium heat, stirring constantly, until the mixture is hot throughout, about 2 min.

Melt the cheese and fill. Turn the heat down to low. Scatter the Parmesan over the meat, then lay the American cheese slices across the top, overlapping them slightly. Let both cheeses melt, about 2 min. Divide the filling evenly among the four split rolls, toasted if desired, and serve straight away.