A pickled onion is an onion which has been preserved in vinegar with spices and jarred. They are an essential part of a traditional British pub meal called a "Ploughman's lunch" which consists of bread, cheeses, cold meats and pickles, but are also eaten throughout the world, either plain, or as an accompaniment to a variety of meals. Recipes for making pickled onion differ from chef to chef but all include onions and a pickling mixture of vinegar of some sort.
The choice of which onion to use for pickled onion is usually decided by which "baby" onions are available. Usually shallots are used, as they are small, but any variety of onion may be used, as long as they are small, so that they can be fitted easily into the pickling jars. The onions are topped and tailed and then peeled. Doing this under water, or keeping a piece of bread in the mouth while peeling them is thought to reduce the tears associated with working with onions. Covering the unpeeled onions with boiling water and allowing it to cool also allows the skins to be rubbed off easily.
Most traditional pickled onion recipes then suggest that the onions are soaked for 24 hours in cold brine, or salty water. To keep the onions completely submerged, a heavy dish, or dish piled with a heavy book should be placed on top of the onions in the brine. Recipes may differ at this point and, if completely crisp pickled onions are desired, once they have been soaked, they are removed from the salty water, dried off and placed in clean, dry pickling jars. Other recipes call for the onions to be added to the hot vinegar mixture, giving a more tender, slightly cooked, pickled onion.
The vinegar and the spices used also differ from recipe to recipe, according to preference. Combinations of spices used may include pickling spice, bay leaves, chili, salt and pepper, cinnamon and ginger. Some chefs also add sugar to the vinegar. The vinegar is heated, in some cases boiled, with the spices, either loose or tied in a muslin cloth for a short period. The vinegar emits strong fumes when heated, so good ventilation is recommended.
Once cool, the vinegar is poured into the jars over the onions. Some chefs leave the spices in the vinegar, while others strain it before pouring over the onions. The jars should not be filled to the brim. They are then sealed and stored in a cool, dry place to allow the flavors to be absorbed. They should preferably be left for at least four weeks before being eaten.
