Place onions in one large jar or
divide them among a number of smaller jars. Using a pestle and mortar, bruise
the peppercorns and all spice, mix with salt and add the mixture to
the vinegar. Pour this spiced vinegar over the
onions until 1 cm of the liquid level is above the onions. Seal with waxed paper or plastic
screw tops. Do not use metal lids, as they
react with the vinegar. Store for at least a month in a
cool, dark place before eating.
