Small baby octopus - about 5cm long - aren't easy to find fresh. You'll probably have to buy frozen ones. Don't try substituting large octopus for this dish - it's too tough. If you can't find the babies, use small squid instead.
Somyeon are Korean thin wheat flour noodles; you can substitute with somen. Gochujang is Korean chilli paste, while gochugaru is Korean chilli flakes. Both can be bought from a Korean grocery, as can sesame (perilla) leaves and banchan (side dishes).
Clean the octopuses (defrosted if frozen) by pulling the body/head away from the tentacles. Remove and discard the guts, and trim off the eyes and beak. Put the octopus in a bowl and sprinkle liberally with salt. Massage with your hands – the octopus will exude a foamy liquid. Rinse thoroughly in a colander and drain. Repeat the process again, and rinse well to wash away the excess salt.
If using squid, from the body pull out the tentacles, quill and innards. Set aside any intact ink sacs, then discard the innards and quill. Cut off and discard the eyes and beak from the tentacles. Remove the purplish membrane from the body – it will pull off easily. Slit open the bodies and scrape away any remaining innards still attached to the flesh.
Bring a large pot of water to the boil, add the octopus/squid and blanch for 30 seconds, then drain. Wash out the pot, then fill it with water and bring to the boil. Add the somyeon (Korean thin wheat flour noodles), or somen, and simmer until done (3 minutes for somyeon, 2 minutes for somen), then drain, rinse with cold water and drain again.
Cut the carrot in half lengthwise and slice it very thinly. Cut the onion in half, then slice about 5mm ( ¼in) thick. Halve the Korean zucchini lengthwise, then slice about 5mm (¼in) thick. Mince the garlic and ginger. Cut the spring onions into 5mm (¼in) pieces.
Mix the gochujang (Korean chilli paste) with the gochugaru (Korean chilli flakes), soy sauce, sugar, garlic, ginger, sesame oil and 60ml (¼ cup) water.
Heat 10ml (2 tsp) of cooking oil in a wok or skillet. Add the vegetables and stir-fry until the onions are wilted. Add the gochujang/gochugaru (chilli paste/chilli flakes) mixture and simmer, stirring often, until the vegetables are about half cooked; if the ingredients stick to the pan, stir in a little water. Stir in the octopus/squid and simmer for about three minutes, or until cooked. Stir often and add water, if needed; the sauce should lightly coat the ingredients. Taste for seasonings and correct if necessary. Stir the spring onions into the octopus/squid and other ingredients then ladle the mixture into a serving bowl.
Lay the sesame (perilla) leaves or vine leaves on a plate, top with small bundles of the noodles and sprinkle with sesame seeds. Let the diners mix the noodles with the octopus and vegetables before eating.