In a large bowl, mix together the garlic, oregano, and 1 tbsp each of the olive oil and vinegar. Season generously with pepper. Add the steak and leave it like this for a few hours, ideally. When you’re ready to grill, season the meat well with salt.
I like to cook the steak as a whole piece, rest it, then slice it to share. This means cooking it over a very hot grill for 2–3 minutes, then flipping it and cooking the other side for 2–3 minutes. Then, move the steak to a cooler part of the grill, flip it again and cook it for another 1–2 minutes, then repeat on the other side. Remove the steak from the grill and rest it on a plate for at least 10–15 minutes somewhere warm. While the steak is resting prepare the onions.
In a pan over a high heat, fry the onion in the remaining olive oil for about 5 minutes (turning brown is good), then add the remaining vinegar and cook over a high heat, until the vinegar has fully evaporated. Season to taste.
When you are ready to slice the steak, spread the bread rolls with the ’nduja and cream cheese. Add the fried onions and put to one side ready for the steak. Slice the steak against the grain into ribbons. The fatter side should be rare and juicy with the thinner side slightly more well-cooked, so that everyone can enjoy it to their liking. Add the sliced steak to the prepared rolls and serve immediately.