A thin curry is nearly always one of three things: too much liquid, not enough simmering, or a thickener that has not had the chance to work. All three are easy to fix, and you can usually save the curry in the pot.
I cook a lot of curry at work, and my own recipes thicken in different ways: a flour roux in my Japanese potato curry, a blended sauce in my mango butter chicken, and the lid off at the end of my Jamaican lamb curry in the slow cooker. Here is what is going on in each, and how to fix a runny one.
The short answer
A curry is too thin when there is more liquid than the thickener can hold. Simmer it with the lid off to drive some of the water away, or add a thickener: cornflour mixed with cold water, a little flour cooked in fat, or some of the curry blended back in. Then give it a few minutes, because a sauce always looks thinner in the pot than it will on the plate.
How to thicken curry
- Take the lid off and simmer. The simplest fix, and the only one that makes the flavour stronger rather than weaker, because you are taking water out instead of adding something. Give it 10 to 20 minutes and stir now and then so it does not catch.
- A cornflour slurry. Mix 1 tablespoon of cornflour with 2 tablespoons of cold water, stir it in and let it bubble for a minute or two. Mix it with cold water first, or it turns lumpy the moment it hits the hot sauce. It is what my lamb curry card suggests when the gravy is thin.
- A roux. Flour cooked in a little oil or butter for a minute, the way Japanese curry is thickened. Stir it in, then let the curry simmer for a good ten minutes. Flour is a weaker thickener than cornflour, so you need about half as much again to get the same result.
- Blend some of it. Lift out a ladle of sauce and vegetables, blend it and stir it back in. My butter chicken sauce is blended smooth before the chicken goes back in, and the onions and tomatoes give it body.
- Crush a few potatoes. If your curry has potatoes, press a few against the side of the pot. Their starch goes into the sauce and thickens it.
- Okra. In my Jamaican lamb curry the okra does some of the work. It gives off a natural thickener as it cooks, which is also why it goes into gumbo.
Why it thickens, then thins again
Starch thickens a sauce by soaking up water and swelling as it heats. Once it reaches its thickest, it slowly starts to thin again if you keep it at a hard boil for a long time or stir it hard. So once the curry has thickened, keep it at a gentle simmer and stir it gently.
Acid can work against it as well. Flour and cornflour cope with the sourness of yoghurt or tomatoes, but potato starch and arrowroot thin out sooner in acid, so if you use them, add lemon or tamarind near the end. And if you make your own roux, keep it pale: the darker you brown the flour, the less it thickens.
Judge it on the plate, not in the pot
A curry always thickens as it cools. Put a spoonful on a cold plate and check it there before you add anything else. It is also why leftover curry is so much thicker the next day: add a splash of water or stock when you reheat it.
Japanese curry that will not thicken
With Japanese curry roux, the usual reason is that the roux went in off the heat and the curry never simmered afterwards. Dissolving the roux is not enough. The thickening happens while it simmers, so give it a good ten minutes on a low heat, stirring now and then. That is how my Japanese potato curry card is written.
The other one catches people out: honey. Honey carries enzymes that break down starch, and starch is what is thickening your curry, so honey stirred in at the end can leave a curry that stays thin however long you cook it. In my recipe the honey goes in with the coconut cream and the pot comes to the boil before the roux goes in, which deals with it.
Too much liquid to begin with
A slow cooker loses almost no liquid, so a curry can come out thinner than it would on the hob. With my lamb curry, if the gravy is thinner than you want, I take the lid off and cook it on high for the last 30 to 45 minutes. Vegetables give off water as they cook too, so if you add a lot of courgette, aubergine or spinach, use a little less stock.
Start with the gentlest fix and simmer it with the lid off. If you are short of time, a cornflour slurry is the quickest. And if it is a Japanese curry, give the roux its simmer.
Why does my curry taste bland?
A thin curry and a bland one often have the same cause: too much water. Every extra cup of stock thins the taste as well as the sauce, which is why simmering with the lid off is the fix I reach for first. If your curry is thin and flat, start there.
If it is thick enough and still tastes of very little, go through these in order.
- The onions went in with everything else. Onions need time on their own in the pan to go soft and sweet, and that sweetness is the base of the sauce. My onion lesson goes through how long.
- The spices or paste were never fried. Flavour dissolves far better in fat than in water, so spices or curry paste stirred straight into liquid never give much of it up. Fry them in the oil for a minute or two first, until they smell strong. In my Thai fish and prawn curry the paste is fried before anything wet goes near it, or it keeps a raw edge however long you simmer it.
- The meat was never browned. Grey meat adds very little to the pot, a dark crust adds a lot. My lesson on browning meat shows how.
- Not enough salt. The most common one. Salt does more than make food salty, it also takes the edge off any bitterness. Add a little, stir, taste and add more if it needs it. If there is fish sauce or soy in the recipe, add more of that before plain salt.
- No sourness at the end. A squeeze of lime or lemon, a spoon of tamarind or a little yoghurt, stirred in right at the end, wakes a curry up. In my Thai curry the lime is not a garnish.
- Old spices. Ground spices lose their smell within a few months. If the jar barely smells when you open it, it will barely taste of anything in the pot.
FAQ for Thin Curry
Can I thicken curry without cornflour?
Yes. Simmer it with the lid off, stir in a little flour cooked in oil or butter, blend a ladle of the sauce back in, or press a few cooked potatoes against the side of the pot. Simmering is the one I reach for first, because it makes the flavour stronger.
How long does it take for curry to thicken?
A cornflour slurry needs a minute or two at a bubble. A flour roux needs about ten minutes of gentle simmering, and simmering with the lid off takes 10 to 20 minutes. Whatever you use, check it on a cold plate, because a curry always thickens as it cools.
Why did my curry get thinner after I thickened it?
Starch thins out again if the curry keeps boiling hard or you stir it a lot. Once it has thickened, turn it down to a gentle simmer and stir gently. Acid does the same, so add lemon or tamarind near the end.
Why is my Japanese curry watery even with the roux?
Usually the roux went in off the heat and the curry never simmered afterwards. Dissolving it is not enough. Give it ten minutes on a low heat, stirring now and then.
How do I make curry taste better?
Taste it before you serve it and fix it in this order: salt first, then a squeeze of lime or lemon, then, if it is still flat, simmer it down a little. Next time, give the onions longer, fry the spices in the oil before any liquid goes in, and brown the meat.
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