Thinly slice the onions and add them, along with all of the remaining ingredients, to a saucepan.
Place over high heat, mix well, and make sure the onions are covered in the brine.
Bring the mixture to a boil, reduce the heat to low, and cook for 1 minute. Remove from the heat.
Transfer the mix to a clean, sterile jar. Seal with the lid and store in the fridge.
Chef's Tips
Slicing the onion as thin and even as possible matters more here than in most recipes — thin slices pickle through evenly in the brief brine time, while thicker pieces can end up under-pickled in the centre.Briefly boiling the onions directly in the brine, as written, gives a softer pickle rather than an ultra-crunchy one — if you prefer more bite, pour the hot brine over raw sliced onion in the jar instead of boiling them together.Let the jar cool to room temperature before sealing and refrigerating — sealing while still hot can trap steam and affect how well they keep.
Storage & Reheating
These are ready to eat once cooled, though the flavour deepens if you leave them a few hours or overnight. Stored in a sealed, sterile jar in the fridge, they'll keep for several weeks.