Remove the steak from the fridge 30 minutes before cooking to bring it to room temperature.

Add the butter and onions to a pan and brown over medium heat for 5 minutes. Reduce the heat, cover with a lid, and cook for 20 minutes. Add the salt and pepper, then cook for another 5 minutes until completely soft and caramelised.

In another pan, cook the garlic over medium heat for 2 minutes. Add the stock pot, water, relish, pepper and thyme, then bring to a simmer. Reduce the heat to low and leave to simmer while you cook the steak.

Season the steak with salt, pepper, stock cube, and a drizzle of olive oil. Heat a pan over medium heat and add the steak. For medium-rare, cook for 4 minutes on one side, turn and cook for 3 minutes on the other side, then render any fat for 1 minute. Adjust the timings if you have a thinner steak.

Remove the steak from the pan and leave it to rest for 5 minutes.

While the steak rests, add the cheese to the ciabatta and cook in the air fryer for 5 minutes at 180C, or in the oven for 10 minutes at 190C.

Slice the steak, add it to the ciabatta, and top with the onions. Serve with the sauce on the side for dipping.