I want to make a curry using mango (frozen as there aren't any fresh mangos where I live). I usually use tomato puree for curries, but I am never happy with the result.
Even after simmering for two hours with generous amounts of spices bloomed in oil it still just ends up tasting like tomato. I tried coconut milk, but it just caused the same issue, but even worse. Is there something I'm doing wrong? Should I use a different liquid?
If you want a curry to taste strongly of mango then the liquid you should use is...mango. Eaten by itself mango is very flavorful, especially when fresh and ripe, the frozen mango I've used is not that strong and can be overpowered by other flavors. So start with mango as the base, and add other liquids like stock, yogurt or coconut milk sparingly.
If it's the spice not coming out then you may need to rethink the definition of generous. Good, strong curry flavor needs good, strong heaps of spices, especially if they aren't fresh or are weak to begin with like you get in many supermarkets. If you can source your spices from an asian supermarket, health food store or anywhere else that they get good quality. Buy small amounts often rather than big packets which then sit around for ages losing flavor.
From what you have shared @ShadySpiritomb, I think the root cause could be the use of frozen rather than fresh mango. Most fruit has a very high water content, and freezing will cause the cell wall to rupture. When defrosted, the fruit will have a mushy consistency, and the flavour may be diluted by any additional moisture captured during the freezing process.
The first thing I would do is defrost your mango in a sieve over a bowl in a refrigerator. That way, you can reheat the flesh separately in the sauce until you reach the correct consistency that you want for your curry. Before doing that, though, I would prepare a basic curry sauce by frying off onions, garlic, and whatever spices etc. you intend to use. Once these have been cooked off, I would add the reserved mango juice and reduce this by 30-60%, continually tasting until you are happy with the balance. By reducing the liquid, you will concentrate the mango flavour.
Once this sauce is ready, add the mango and heat through. Depending on the condition of the defrosted mango, this may not need a long time; if the fruit is really "mushy", heating through will probably be sufficent. If it needs longer to soften, add earlier in the process.
If desired, any tomato or coconut milk etc. should be added after the mango juices have reduced and before you add the mango flesh.
