If you are lucky,as I am, to have a good Chinese supermarket/Hypermarket nearby I can highly recommend Goldfish Brand Authentic Chinese Curry paste.They come in 405gm plastic tubs or you can buy 5kilos of it.
This paste will make any meat,fish or veg taste exactly the same as a Chinese take away curry.I would wager that the take aways use this brand or something like it.
I cut up 2 or 3 onions into large chunks and fry in oil with the chicken or whatever you are cooking.I add the paste according in quantity to the thickness of the sauce you require with water.Simmer until meat is cooked through and add some peas a few minutes before ready to serve.I don't like the onions or peas to be over cooked but retain a little crunch.Sometimes I add a tsp of 5 spice powder during the frying process to give it a little more aniseed flavour but not necessary as the paste has it in any case.You can buy this past on lin if you can't source locally.It really does taste like a genuine take away chinese curry.Good hunting and Bon Appetite.