I always thicken my curry with cashews. You can get them for really cheap at big lots. You can actually thicken a LOT of sauces with cashew, they don't do a lot to the flavor profile but the thickening performed is completely different from what you'd get with flour or corn starch.
Are we talking ground cashews or whole? Also, I'm assuming you mean raw cashews, which are soooo good...
Here, have a recipe!
1 and a half cup of pitted dates
2 cups raw cashews
some (dairy-free) milk
1. Soak the dates in hot water until soft.
2. Grind the cashews in a cuisinart until fine. Set aside half a cup.
3. Add the dates to the cashews and process until mixed. Add some milk to bind the mix.
4. Make the resulting paste into little balls and roll them in the cashews you set aside.
5. Chill the balls for an hour.
6. OM NOM NOM NOM NOM
I've refined my curry into an almost commercial level product using some advice I picked up from an indian celebrity chef's channel on youtube. I take all my base ingredients aside from the stuff I want to be chunky and blend it in a commercial blender the in-laws bought on impulse. (An old Osterizer will work just as well, if you can find one made before the 70s) When I do this I throw the cashews in and blend until it's smooth and just a little airy.
After that I pour the curry back into the pot, add the chicken or lamb or beef (which I coated in yogurt and spices and seared prior) and whatever else I want in there (Cauliflower and/or Potato usually) and cook them together for about 30 minutes with the lid on. If I'm making butter chicken or tikka masala (or even vindaloo) I usually add about 2-3 tbsp of Ketchup. (more advice from indian celebrity chef) I prefer Ketchup to straight up sugar.
If I'm making something I want to have a specific texture, of course, I don't use the blender. This is the case with, say, Korma, where I mash up most of the ingredients and hand crush the spices and cashews for a more coarse texture. I got this idea from an indian cookbook. It's time consuming, which keeps the Korma from being a regular thing - strictly a birthdays and anniversaries dish - but the quality is hard to beat.
I stopped making curry for six months after my trip to Michigan, because
noone in my family except my grandmother enjoyed my curry, and she couldn't eat it because the blood thinner she was on restricted her from eating garlic, ginger, onion or cauliflower. I'm beginning to get a taste for it again, it's one of the things I really enjoy cooking and eating, and everyone who lives here appreciates it at least.