In a small bowl, whisk together dressing ingredients and set aside.
Bring a large pot of salted water to the boil. Add soba noodles and cook for 4 minutes (or according to directions on the packet). Drain well then transfer to a large bowl. Reserve about 3-4 Tbsp of the dressing then add the rest to the warm soba noodles and mix well to coat all the noodles. Allow to cool.
Place cooled noodles in a serving bowl with cucumber, sugar snap peas, snow peas, spring onions, radishes and coriander. Toss to combine. Gently flake over smoked salmon. Drizzle over remaining dressing and sprinkle over sesame seeds. Serve immediately.