First of all shred the cabbage into ¼ inch (5 mm) pieces, then place the frying pan over direct heat and dry-fry the pancetta or bacon until crispy and golden – about 5 minutes – and remove it to a plate.
Now add the oil to the pan and, when it's hot, fry the onions over a medium heat for 5 minutes: they also need to be turning golden brown at the edges. Now turn the heat up to its highest setting and add the cabbage, stirring continuously for about 3 minutes, keeping it on the move and tossing it around.
Return the pancetta or bacon to the pan and add the apple, garlic, bay leaf and thyme, seasoning well with salt and black pepper. Toss the mixture around for a few seconds, then add the cider and cider vinegar and continue to cook, with the heat still high, for 1-2 minutes. Finally, remove the bay leaf and thyme, taste and season and serve as soon as possible.