Take the skin and meat off the duck, chop it into bite-sized pieces and set aside.
Heat the oil in a wok, add the curry paste and fry, stirring, for 2 minutes or until it is fragrant. Add the coconut milk, stock, ½ tablespoon sugar and 1½ tablespoons fish sauce and simmer for 2 minutes.
Add the duck, kaffir lime leaves, peas, tomatoes and pineapple and cook for another 4–5 minutes, stirring occasionally. Taste and adjust the seasoning, using the rest of the sugar and fish sauce if necessary.
Serve with the extra pineapple and noodles, if liked, garnished with a few slices of red chilli and spring onion strips.