Preserved shallots in malt vinegar vinegar make a classic condiment that will never ge. Place the onions in a large heatproof bowl and pour over boiling water to cover.
Once cool, trim roots and tops and peel. Sprinkle the salt over the peeled onions, stir and leave overnight. Next day rinse the onions well and dry with kitchen towel. Place the vinegar and honey into a large pan and gently heat just to dissolve the honey into the vinegar, but do not boil.