Filets de maquereaux moutarde a l'ancienne

mackerel fillet (56%), water, mustard (9%), (water, mustard seeds, alcohol vinegar, salt) sunflower oil, alcohol vinegar, old-fashioned mustard (2.2%) (water, mustard seeds, alcohol vinegar, salt) apple cider vinegar, processed corn starch, salt, spices, dehydrated shallots, thickeners, xanthan gum and guar gum,