Cook the noodles in boiling salted water according to the packet instructions, then drain, reserving a mugful of cooking water. Meanwhile, finely grate the zest of 1 lime, snip the cress and put both aside.
Toast the sesame seeds in a dry non-stick frying pan on a high heat for 1 minute, tossing regularly. Reserving one quarter of the seeds, pound the rest in a pestle and mortar until fairly fine, then muddle in the teriyaki and the juice of 1 lime. Taste, season to perfection with sea salt and black pepper, and you’ve got a black tahini!
Toss the noodles and black tahini together, loosening with a splash of reserved noodle water. Serve sprinkled with the lime zest, cress and reserved seeds, with lime wedges on the side, for squeezing over.