For the dashi stock, put the ingredients in a pot and bring to a boil. Skim off any foam and simmer for 10 minutes, then strain.

For the soup base, in a separate pot from the dashi, add the ingredients and heat until just before boiling, dissolving the sugar.

Scrape the skin off the burdock root and slice it thinly on the diagonal. Lightly soak in water and drain.

Peel the taro root and slice into rounds. Cut the carrot and daikon into quarter rounds.

Heat sesame oil in a pot and sauté the burdock, taro, carrot, and daikon. Add 3 1/3 cups (800 ml) of dashi and sake, skim off any foam, and simmer on low heat for about 15 minutes.

Once the vegetables are tender, add the soup base and warm through.

Cook the soba noodles according to package instructions, rinse with water, and drain.

Pour the soup over the soba noodles, top with green onions, and serve.