Place the pumpkin in a steamer over a saucepan of simmering water. Cover and cook for 15 minutes or until tender.
- Meanwhile, heat the oil in a wok over medium heat. Add the laksa paste and cook, stirring, for 2 minutes. Add the stock and coconut milk, and stir to combine.
- Bring the coconut milk mixture to a simmer over medium heat. Add the prawns and beans. Cook for 3-4 minutes or until the prawns are just cooked through. (To freeze, see notes)
- Add the pumpkin to the coconut milk mixture and cook for 1 minute or until heated through. Stir in the fish sauce.
- Meanwhile, place the noodles in a large heatproof bowl. Add enough boiling water to cover. Set aside for 10 minutes or until soft. Drain.
- Divide the noodles among serving bowls. Pour over the coconut milk mixture and top with the coriander, mint, bean sprouts and chilli, if desired. Serve with lime wedges.