Dice the peeled and de-seeded squash in to bite-sized pieces and steam until tender to the knifepoint - around 10min but may vary depending on steamer/how densely packed etc.
Trim the ends of the beans and cut longer ones into shorter pieces and steam them as well - they will be quicker so it's best to do them separately, or you can boil them around 3-5min until just tender.
Cook the noodles according to the packet instructions and divide between two bowls.
Meanwhile prepare the spice paste - peel the ginger and cut into chunks, take the end of the chilies and remove seeds if you want it less hot, leave in if you want hotter, and roughly chop the cilantro and salad/spring onions then put all the paste ingredients (lime zest, cilantro, salad onions, chilies, ginger, lemongrass, sesame oil, ground coriander and turmeric) in a small food processor/blender and blend until a fairly smooth paste. A few lumps are fine.
Heat the oil in a wok or skillet/frying pan and fry the spice paste for a minute or two, stirring regularly. Add the coconut milk and stock and bring to a simmer. Add the soy sauce, fish sauce (if using) and lime juice as well as the squash and beans. Cook for a couple minutes to allow the flavors to mingle. Adjust the lime/soy to taste if needed.
Carefully divide the vegetables between the bowls and pour over the broth/sauce.