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Onion Sauce

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Onion sauce for curries

Onion sauce for adding to curries.

British Indian Restaurant (BIR) style onion sauce is super easy to make but takes a long time so plan ahead.

This onion sauce is part of what makes do piazza curries so good. It can also be added to other curries for extra flavour.

The secret to success is in the slow cooking. I usually cook my onion sauce in a low oven over night. Doing this gives the sauce more depth. You can use the finished onion sauce exactly as it is when you take it out of the oven or blend it if you prefer smoother curries.

When you take the finished sauce out of the oven, the top will be slightly blackened. Try it. If you like the flavour, stir it in. If not, skim it off the top.

Making onion sauce

I used four onions this time around.

Making onion sauce

Slice the onions thinly and then place in a pot.

Making onion sauce

Add about two chopped red bell peppers.

Making onion sauce

Stir in the fennel powder and cloves.

Making onion sauce

Cover with curry base sauce and a little water. About 200ml water should do.

How To Make A Tasty Onion Sauce To Add To Your Curries

How To Make A Tasty Onion Sauce To Add To Your Curries
Prep Time 15 minutes
Cook Time 10 hours
Total Time 10 hours 15 minutes


  • 4 onions - finely sliced
  • 2 red bell peppers - finely sliced
  • Curry sauce - enough to cover plus about 200ml water
  • 1 teaspoon fennel powder
  • 3 whole cloves


  1. Slice the onions so that the are paper thin. You want to almost fill the pan you are using with the onions.
  2. Slice the red bell peppers and place them on top of the onions to fill the pan.
  3. Add the fennel powder and cloves and cover.
  4. Now add the base curry sauce so that it covers the onions and about 200ml water.
  5. Place on a low heat and bring very slowly to a simmer.
  6. This is when I place the onion sauce in the oven on the a very low temperature with the lid on. You can leave it there all night if you like. The longer you cook the sauce the better up to about ten hours.
  7. The top of the sauce will be quite blackened when you take it out of the oven. Try it. If you like it, stir it in. If not, remove the blackened bits.
  8. Place the finished sauce in a blender and blend until smooth or leave it chunky as it is.
  9. Use immediately or freeze.

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Anne Macdonald

Saturday 3rd of October 2020

Hi Dan

What else can this onion sauce be used in? I have made a batch today (its gorgeous btw) but there is soooooo much of it & I only need a few hundred grams for the Dopiaza. Obviously I'll freeze it but dont want to live on Dopiaza for the rest of the year lol.

Many thanks Anne

Dan Toombs

Sunday 4th of October 2020

You can serve the onion sauce in any curry really. Just add a little to any curry you make and then add more to taste. Thanks Dan

Anne Macdonald

Saturday 3rd of October 2020

I've made your base sauce today & frozen in 300ml portions. I've made the onion sauce too but have cooked it on the hob rather than the oven, is that ok? I only managed to do 5 hours though because I need to cook a curry for this evening, it looks watery but i haven't blended it yet. My son had us over last week to sample their Misty Ricardo curries, I googled the recipes for the base gravy & onion sauce and found yours instead, I hadnt realised it was different until my Son told me. We are very interested now to compare. I must say I love your videos & printable recipes so Im looking forward to our 1st curry tonight, a chicken tikka Dopiaza. Thank you for your inspiration.. It would be great btw if people could upload photos of their attempts on here.

Dan Toombs

Sunday 4th of October 2020

Great to hear! Thanks very much. Dan

Neil Biddulph

Saturday 4th of July 2020

Hi Dan could i do the onion sauce in a pressure cooker at all just dont like the idea of cookwr being on in the night

Dan Toombs

Wednesday 8th of July 2020

Hi Neil Yes, you could certainly use a pressure cooker. Thanks Dan


Sunday 25th of February 2018

Hey Dan, I think your recipes are amazing, first I've made Chicken Tikka Masala and now I'm making dupiaza, your recipe says to put onions on a low heat in the oven, what do you mean by low exactly? 80'? 100'?50?!

Cheers, Chris

Dan Toombs

Tuesday 27th of February 2018

Hi Chris

About 80c should do. Hope that helps and thank you.



Tuesday 2nd of January 2018


Im attempting my onion sauce in the slow cooker for the first time tonight, so that i can make dopiaza tomorrow.

I will let you know how it goes - i suspect it might taste too 'raw oniony' but im sure itll still be edible.

Also... I didnt have red Peppers so ive swapped it for whatever else i had.... Which was 2 super ripe plums and a tomato. I thought it might have the same level of sweetness. We'll see!!

Dan Toombs

Monday 22nd of January 2018

Hi Claire. How did it go?


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