What are substitutions for coconut in curry?

Thai curry recipes often use a lot, and the flavour is distinctive. You'll need to experiment. Your idea of cashews is a good place to start. What I've often used in Indian curries is ground almonds (almond flour would be better but I can't get it easily). They have some thickening power and quite a suitable taste. You could also try cooking with nut milk - I've only done this a couple of times because it's not something I normally have, but recently used some almond milk in a sauce with lentils etc. It ended up with a fairly creamy texture. This was a brand marketed for cooking and a little thicker than I've come across before

As an aside, I hope you've had medical confirmation of the allergy - it's not exactly unknown for these things to be deceptive.

Substitutes have been mentioned already, but how about going the other way?

There are more curries without coconut than there are with it. Many many curries use an onion base for thickness; coconut is a Southern Indian/Sri Lankan twist on what is a continent-full of cuisine.

Look down the even just the standard sauces of any take-away menu...
Bhuna
Madras
Vindaloo
Jalfrezi
Rogon Josh
Dopiaza
Pathia
Dansak
The list goes on... & not a coconut in sight.

Or for more variety, how about Ethiopian Wat, or a Moroccan Tagine?
For Thai, have a look at a Jungle Curry - again, no coconut.

I don't know much about Thai curries but there are plenty of Indian curries that are broadly similar to coconut-based ones but with sauces made with cashews and other nuts. Typically, you'd want to soak the nuts for a few hours and then blitz them into a puree, or just use a nut butter because life's too short.

Indeed, there are many Indian curries that don't use coconut or any other nut. Coconut is basically a south-Indian thing and being allergic to coconut doesn't stop you eating Indian food, just like being intolerant of pasta wouldn't stop you eating European food. I suggest you get yourself a good Indian recipe book. I'm a huge fan of Camellia Panjabi's 50 Great Curries of India, because it has a pretty long introductory section that explains what all the different ingredients are for, which is really helpful when, for example, you can't eat coconut but you want to make something similar.

We cooked a lot of vegan at home for some time and often used soy cream as substitution for sauces that demanded cream. It has a unique taste, but I do not find it unpleasant. It has about the same thickness as coconut and I think the taste is also quite fitting for curries. As others mentioned, some almonds or cashews could enhance the experience. In Germany, I usually find this soy cream in the vegan/non-dairy aisle next to the other soy products.

As we do not know exactly what you allergic to (you said coconut but it could be coconut milk, an additive in the milk or coconut in general), I will make some extra suggestions:

1) You might be able to try adding natural coconut flavouring to the already mentioned nut milks (cashew or almond). This might tip the scales in making an Indian style almond based curry taste like a Thai coconut milk based curry.

2) If you are allergic to everything coconut then you could try Imitation Coconut Extract which shouldn't contain any coconut. Again, this might tip the balance on the other nut-based milks.

3) You could try adding gorse flower extract. I have never tried it but I do know from roaming the coastlines and moorland of Devon, that gorse smells a lot like coconut. It is edible, is common year-round and according to eatweed.com, has a subtle coconutty taste. I see no reason this could not be added to a curry to infuse further coconut tones.

Finally, if you are allergic to all coconut, here is a quick and helpful guide to replacing all coconut ingredients.

I can only speak to south indian curries. I don't have a substitute for coconut but you can certainly make a great curry without dairy or coconut added to the mix. You can make a delicious sauce from just water and emulsified fats combining with your choice of spice meats and veg.

I have only experience with meat based dishes so this may not work out for any vegetarian attempts. Meat releases fat and water when covered and heated. After I sauté the veg (typically ginger, garlic, onion), I add the meat which has been marinating in spices and oil (or just dry rubbed with spices). I cover the pot and keep the heat on high for a few minutes until I see water appear at the bottom of the dish. Then I reduce the heat to med low and leave it covered for 30 mins or so. Over time more water and fat is released and the meat should be practically swimming. From there I simmer uncovered for as long as I need to thicken the mixture. This also concentrates the flavors.

Chicken stock also can be added. Even plain water. You'll also get water from watery veg like tomatoes. I'm pretty sure you could add kool aid if you wanted to. Most of the flavor comes from the spices and chillis.

North indian and Pakistani food uses a combination of onions, tomatoes and ginger garlic paste to form the curry base. First you fry some finely chopped onions until they turn golden brown, then add about a tablespoon of ginger garlic paste, finely chopped tomatoes and the spice powders (chilli powder, turmeric etc.). You let that cook stirring from time to time until the tomatoes turn into a slurry. That's your curry base! There are many videos on youtube that show you how to make this in case you want to see it in more detail. It's also possible to substitute yoghurt (curd) for tomatoes.

From my reading and research, I've found that there are organic non-dairy yogurt alternatives available. There is also silken tofu that may be used to replace the coconut. They do state that it is dependent upon how creamy you want your dish to be., as the yogurt and tofu would make the dish much creamier. As I believe was mentioned above, there are other non-dairy milks that can be used and can be thickened slightly be adding a bit of arrowroot (or similar) flour. (Also found in my research). I've studied this for years for personal use because many people, like me, are allergic to coconut AND to tree nuts.