Chop the leek, garlic ginger and simmer in oil on low heat with the red curry paste until transparent. Add the chopped prawns, diced peppers, chopped pineapple and toss. Increase heat and before vegetables starts browning add the pineapple juice and coconut milk and simmer by half. Crush the nuts and chop the coriander, meanwhile boil the pasta drain well than add to the sauce toss and mix in the cashew and coriander.