RealGravy

Onion Gravies

Caramelised Red Onion Gravy

Red onions taken dark and jammy with a pinch of bicarbonate of soda to speed things along, sharpened with red wine vinegar and thickened by reduction rather than flour.

  • Contains meat
  • red onion
  • caramelised
  • steak
  • burgers
  • no flour
Illustration of Caramelised Red Onion Gravy
Prep
10 min
Cook
40 min
Total
50 min
Serves
4
Difficulty
Medium

Red onions have more sugar and less bite than brown ones, so they go jammy rather than savoury. That makes this gravy sweeter and darker, closer to a chutney in flavour, and it is brilliant with anything chargrilled. The bicarbonate of soda is a proper kitchen trick, not a gimmick, and it cuts a good ten minutes off the browning.

Ingredients

Makes about 400ml, enough for four plates

Scale

Kit

  • Wide frying pan
  • Wooden spatula

Method

  1. Heat the oil in a wide frying pan over a medium heat. A wide pan matters here because you want the moisture out of the onions fast, and a crowded saucepan just steams them.

  2. Add the onions and a good pinch of salt and stir for 5 minutes until they start to slump. Sprinkle over the bicarbonate of soda and stir. Within a minute they will darken noticeably and go slippery. That is the alkaline speeding up the browning reaction, and it is meant to look like that.

  3. Turn the heat to low and cook for 20 to 25 minutes, stirring every few minutes. They will lose their purple and go a deep mahogany, sticky and reduced to about a third of their original volume.

  4. Add the sugar and let it melt into the onions for 2 minutes, then pour in the vinegar. It will hiss and steam. Scrape the base hard while it evaporates, which takes about a minute, and the pan will come clean.

  5. Pour in the stock, add the bay leaf and bring to a brisk simmer. Let it bubble away uncovered for 12 to 15 minutes, until it has reduced by roughly a third and thickened enough to coat a spoon. No flour, no cornflour, just patience.

  6. Fish out the bay leaf, taste and season. If it tastes too sweet, another splash of vinegar will pull it back into line.

Tips worth knowing

  • Do not be tempted to double the bicarbonate of soda. A quarter teaspoon speeds up the browning, half a teaspoon makes the onions taste of soap and go unpleasantly mushy.
  • This one benefits from a rest. Made an hour ahead and reheated, the sweetness and the sharpness settle into each other.
  • If you want it thicker without flour, keep reducing. It will happily go down to a glaze that you can spoon over a steak.
  • Red onions vary a lot in sugar. Taste before you add the sugar and you may find you only need half of it.

Change it up

  • Add a sprig of rosemary with the stock for something that suits lamb steaks and merguez sausages.
  • Swap half the stock for a light red wine, reduced hard before the stock goes in, for a richer version that suits a good steak.

Keeping and reheating

Fridge for 5 days, and it is one of the few gravies that arguably improves on day two. Freezes for 3 months. Reheat over a low heat with a splash of water, as it thickens up a lot when cold.

Questions people ask

Does bicarbonate of soda really caramelise onions faster?

Yes. It raises the pH, which speeds up the Maillard browning reaction, and you can save roughly ten minutes on a batch this size. The trade off is texture, because the onions break down more and go softer, which is fine for a gravy but not for something like a tart.

Can I use red onion gravy on a roast dinner?

You can, but it is sweeter and fruitier than a classic brown onion gravy, so it tends to sit better with lamb, sausages and steak than with a plain roast chicken. If you want it for a Sunday, cut the sugar and add an extra splash of vinegar.

Why did my red onions go grey?

The pigment in red onions turns dull blue grey in alkaline conditions, which is exactly what the bicarbonate of soda creates. It looks alarming for a minute or two but the vinegar and the long browning bring the colour right back to a deep brown.