The Best Caramelised Onion Relish

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Yield: Makes 5 x 250ml jars


  • 2kg onions, finely sliced
  • 50g butter
  • 2 tablespoons olive oil
  • 2 tablespoons grated fresh ginger
  • 30g packet yellow mustard seeds
  • 1 bay leaf
  • 1 x 5cm sprig rosemary
  • 750g brown sugar (3 1/2 cups)
  • 375ml balsamic vinegar (1 1/2 cups)


Place the onions, butter and oil in a saucepan and cook over a gentle heat until onions are tender.

Add the remaining ingredients and stir until the sugar dissolves.

Bring to the boil and simmer until dark in colour and jam like in consistency.
It should take an hour or so but if you increase the ingredient quantity it will take longer.

Pour into sterlised jars and seal.


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11 thoughts on “The Best Caramelised Onion Relish

  1. Hi there
    Just wanted to check the sugar amount. It seems like a lot compared to most other caramelised onion relish recipes (which on the whole seem to use about half as much (or less) for the same quantity of onions). Could I therefore get away with using less?

  2. Approx how long will this keep for in sealed jar ?
    Also if properly sealed can it be kept in a cuboard until opened ?

    Recently started making chutneys and haven’t made an onion relish yet :)

    • Hi Sue, I wonder if it is a bit sweet and vinegary for using in a tart.
      Maybe better to just caramelise onions separately with a splash of balsamic and some brown sugar.

  3. Forgive me. But what exactly do you do with the “sprig of rosemary”? Do you run your finger over it so all the bits of rosemary fall off and throw away the stick and then sprinkle it through?? Sorry, I realise people are rolling their eyes!

    Approximately how long is the simmering process?

    I really want to have a go at this!

    • Hi Karyn, you simmer it for about an hour or more if you increase the recipe.
      The rosemary can be left on the sprig and the flavour will permeate or you can take the needles off if you like and let them disperse through the relish.