Heat the oven to 200C/fan 180C/gas 6. Whisk together the soy, sesame oil, gochujang and mirin in a small bowl, then pour over the celeriac in a small baking tray. Toss well and roast for 35-40 minutes until the celeriac is sticky and glazed.
When the celeriac is almost ready, cook the noodles following pack instructions, then rinse under cold water. Put the cucumber in a bowl and toss with the vinegar and maple syrup.
Add the cooked noodles to the baking tray and toss with the celeriac and gochujang sauce. Add 1-2 tbsp of just-boiled water to loosen the sauce and coat the noodles. Mix well until everything is combined and saucy.
Divide the noodles between bowls, top with the pickled cucumber, edamame, radishes and spring onions. Scatter with the sesame seeds and herbs to serve.
