How to make a French style escabèche marinade (mackerel escabeche)

From a channel Lumen includes in full: French Cooking Academy teaches classical and regional French home cooking, sauces and technique with the history of each dish, in step-by-step recipe lessons.

A 10-minute video from French Cooking Academy's catalogue; the title names its topic.

Video by French Cooking Academy, played through YouTube's embedded player.