In a food processor, or using a pestle & mortar, blend the paste ingredients together to form a smooth paste. If you're using a pestle & mortar, add each fresh item separately in the order they're listed then stir in the powdered items. It's hard work, but no pain no gain etc.
To make the curry
Heat the oil in a wok, and over a medium heat and when hot, add the curry paste. Sizzle for 30 seconds, stirring to avoid sticking before adding 1/2 the coconut milk.
Let this bubble for 5 minuets to reduce, stirring regularly.
Add the remaining coconut milk, salt, fish sauce and sugar and stir well.
Tip in the vegetables and simmer for 2-3 minutes until just soft before adding the cooked chicken. Stir and remove from heat.
Squeeze over lime juice and test for salt/fish sauce - adjust as you see fit! I always serve mine with plenty of jasmine rice.