Peel and cut daikon radish, carrot and yam (potato) into icho-giri or ginkgo leaf shape. (Scroll down and see "cutting vegetables".) As for burdock, shred like the "sogi-giri" . Cut pork into bite-size. Heat salad oil in a pot and sauté the meat and vegetables. Add water and dashi powder. (If you like lighter taste, skip sautéing and just put raw ingredients in the water to boil.) Bring to boil. Skim off the scum that rises to the surface. Add sake (if you chose to use it). When ingredients are cooked, reduce or turn off the heat and dissolve miso into the soup. Turn the heat up very briefly and remove from heat as soon as it starts boiling. Do not boil too long after adding miso to the soup. Sprinkle minced scallion on top and serve.