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Caramelised onion jam in a glass jar with thyme, served on toasted bread on a white timber table, styled with balsamic vinegar and olive oil in soft natural light.

Caramelised Onion Jam with Balsamic Vinegar

Slow-cooked until sticky, sweet, and deeply savoury, this onion jam is the ultimate condiment. Perfect for cheese boards, burgers, sandwiches, tarts, or to elevate any meal in minutes.
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Prep Time:15 minutes
Cook Time:1 hour
Course: Condiment
Cuisine: Australian, Western
Keyword: balsamic onion jam, caramelised onion jam, homemade onion jam, onion jam recipe, sticky onion jam
Servings: 1 1 /4 cups
Author: Kate Brodhurst

Ingredients

  • 2 tablespoons olive oil
  • 30g butter
  • 1kg brown onions, thinly sliced
  • ½ teaspoon salt
  • ⅓ cup brown sugar
  • ⅓ cup balsamic vinegar
  • 2 teaspoons fresh thyme leaves (optional)
  • ¼ teaspoon cracked black pepper

Instructions

Cook the onions

  • Heat the olive oil and butter in a large, wide saucepan over medium heat. Add the sliced onions and salt, then cook for 10 minutes, stirring occasionally, until softened and translucent.

Caramelise slowly

  • Reduce heat to low and continue cooking the onions for 30–40 minutes, stirring regularly, until they are deeply golden, very soft and starting to stick slightly to the pan. Don’t rush this step, slow cooking is what builds the flavour.

Add sweetness and acidity

  • Stir in the brown sugar and balsamic vinegar. Cook for a further 10–15 minutes, stirring often, until the mixture is thick, glossy and jam-like.

Finish and season

  • Stir through thyme (if using) and black pepper. Taste and adjust seasoning if needed.

Cool and store

  • Allow to cool slightly before transferring to a clean jar.

Notes

  1. COOKS NOTES:
    Oven Temps:     Oven temperatures are for conventional, if using fan-forced (convection), reduce the temperature by 20˚C.
    Measurements: We use Australian tablespoons and cups: 1 teaspoon = 5 ml, 1 tablespoon = 20 ml and 1 cup =  250 ml.
    Herbs: All herbs are fresh (unless specified) and cups are lightly packed.
    Vegetables: All vegetables are medium size and peeled, unless specified.
    Eggs: We use extra-large size and eggs are 55-60 g each, unless specified.
  2. Slice onions evenly – Ensures they cook at the same rate, preventing some from burning while others are still undercooked.
  3. Cook slowly over low heat – Patience is key. Slow caramelisation develops deep, rich flavour and a glossy texture without burning the onions.
  4. Adjust sweetness and acidity – Brown sugar adds sweetness, balsamic vinegar adds balance. Taste and tweak depending on your onions and personal preference.
  5. Optional flavour boosters – Add crispy bacon at the start for a smoky kick, chilli flakes for heat, or a teaspoon of wholegrain mustard for an extra savoury note.
  6. Storage tips – Keep in a clean, airtight jar in the fridge for up to 2 weeks. Always use a clean spoon to prevent spoilage.
  7. Versatile uses – Works beautifully on cheese boards, in burgers and sandwiches, as a glaze for roasted meats, or stirred into tarts and quiches.
  8. Make ahead – Can be made a few days in advance; flavours improve as the jam sits and melds.