Gently fry 3 teaspoons of the curry paste in a wok or saucepan with the garlic and ginger, using sunflower oil (or sesame oil), for one or two mins. Chuck in the chopped shallots, whole button mushrooms, carrots and beans. Stir fry the whole lot until the veg is just about cooked.
Very finely slice about 1 of the lemongrass and chuck that in. Add a splash of Thai fish sauce if you have it. Keep cooking it. Add half a cup of stock and keep cooking it. Add most of a can of coconut milk and the juice of the lime, and gently start reducing the mixture.
When it is all combined and curry consistency has been achieved, chuck in the prawns, in just a minute or two they will be cooked. Do not over cook them! Turn off the heat.
Finally, add two handfuls of roughly chopped coriander and the finely chopped lime zest.
Serve with buttered rice.
