Add 200 ml olive oil to a frying pan over high heat.
Fry the sardines for a few seconds on each side.
Remove the sardines, reduce the heat, and sauté the finely julienned carrot, onions, and leeks in the same pan, adding the sprig of thyme and peppercorns (add additional olive oil if necessary).
When the vegetables are tender, add Jang with Vinegar and sherry vinegar. As soon as the strong vinegar scent has evaporated, remove from heat, add the sardines to the still-hot pan, and allow them to soak up the escabeche flavors.
Place the sardines with the vegetables into glass jars until ready to serve. Escabeche may be served cold or warm.