• Cut the onions in half, peel them and then cut them into 1cm (just under ½") thick slices.
• Heat a 28cm or 11" frying pan over a medium-low heat, add the beef dripping, and when it melts, add the onions. Cook gently for at least 1 hour, stirring every 15 minutes or so, decreasing this time as you get to the end of the cooking process.

  You want the onions to colour slowly, so if they colour quickly, reduce the heat a little.
• When the onions are a nice deep golden colour, turn up the heat to medium-high, pour in the beef stock and stir until the stock has almost completely evaporated. Once this has happened, reduce the heat to low whilst you cook the steak.
• Whilst the stock is evaporating, heat a 30cm or 12" heavy-based frying pan over a high heat.
• Rub the steak with the oil, then season generously with salt and pepper.
• Add the steak to the hot pan and let it sit for 90 seconds, then flip and let it sit for 60 seconds. Add the butter, and when it melts, cook the steak for another minute, basting it with the butter.

  Remove and rest for 7-10 minutes (this will deliver a lovely rare steak). See below for internal temperatures to aim for to get the steak done to your liking.
• Whilst the steak is resting, crumble the Stilton cheese.
• Return the pan you cooked the steak in to a medium-high heat, and when the butter is hot, cut the ciabatta bread in half and toast (cut side down) it in the butter for 2 minutes or until it is nicely golden.
• Thinly slice the steak. Adding the steak's resting juices to the caramelised onions at this point is a good idea!
• Build your sandwich, I start with loads of rocket on the base, then add half of the onions and half of the Stilton, pile on the beef and add the remaining onions and cheese before cutting in half and serving.

Internal temperatures to remove steak to get it done to your liking!

• Rare: The target temperature to remove the steak is 45-47°C or 113-117°F. The final temperature after resting will be 49-51°C or 120-124°F. Estimated total cooking time (3-4 minutes).
• Medium Rare: The target temperature to remove the steak is 48-54°C or 118-129°F. The final temperature after resting will be 52-58°C or 125-136°F. Estimated total cooking time (4-5 minutes).
• Medium: The target temperature to remove the steak is 55-57°C or 130-135°F. The final temperature after resting will be 59-61°C or 137-142°F. Estimated total cooking time (5-6 minutes).
• Medium Well: The target temperature to remove the steak is 58-63°C or 136-145°F. The final temperature after resting will be 62-67°C or 143-152°F. Estimated total cooking time (6-7 minutes).
• Well Done: The target temperature to remove the steak is 64-71°C or 146-160°F. The final temperature after resting will be 68-75°C or 153-165°F. Estimated total cooking time (8-10 minutes).