To make the Laksa sauce, place the onion, butternut squash, garlic, ginger, curry powder, lime leaves, lemongrass, crumbled fish stock cube, coriander, and boiling water into a pan over medium heat. Reduce heat to simmer for 15 minutes or until squash is very tender.

Remove pan from heat and use an immersion blender to whizz the sauce until smooth. Stir in the soy sauce and fish sauce.

Meanwhile, cook the noodles according to the package instructions. Drain well and set aside.

Spray a non-stick work or large frying pan with cooking spray and place over high heat. Add the prawns and stir-fry for 1-2 minutes or until just cooked. Transfer the prawns to a plate and set them aside.

Spray the wok with more cooking spray and stir-fry the vegetables and chillies if using, with a splash of water for about 3 minutes.

Add the noodles, prawns, and Laska sauce to the wok, and stir-fry until the prawns are cooked through and everything is piping hot.

Remove from the heat and stir in the yogurt.

Divide between four bowls and sprinkle with coriander if using.