Gather the ingredients.
Sprinkle the salt over the dry, peeled onions.
Stir to make sure the salt is distributed. Cover, refrigerated overnight (do not leave longer than overnight if you want your onions to be crisp).
When ready, rinse the onions and dry with kitchen or paper towels.
Place the malt vinegar, sugar, coriander seeds, mustard seeds, black peppercorns, and dried chili flakes in a large stainless steel pot.
Heat on medium to dissolve the sugar, but do not boil.
Pack the onions into clean, sterilized jars (about two wide-mouth, quart-size canning jars, or smaller jars, if desired).
Pour the vinegar-spice liquid over the onions to fill the jars, making sure each jar has pickling spices and that there are no air pockets.
Seal the jars and let cool. Store refrigerated. The onions will be ready to eat after about one month.
Peeling pickling onions is fiddly and time-consuming. To speed up the process, cut off the top and tail of the onions.
Then place the onions in a large heatproof bowl and pour boiling water over to cover.
Drain the water after 10 minutes, and presto, the skins will just rub right off.
Do not leave in the water too long or the onions will start to go mushy when you preserve them. Dry the onions with a kitchen towel or paper towels. Proceed with pickling.
