Begin with very cold water in pot. Submerge the Kombu in pot for 30 minutes. When ready to heat the water, add ginger coins. Turn on heat to med-high. Before water boils, take out Kombu. Do not let water boil.
Put DIFFUSER under pot IF you need to keep soup hot. Do NOT put in Miso until you are ready to serve.
Take some of the hot water in a bowl and whisk in all Miso until well mixed. Pour mixture back into pot. Never allow miso to boil.
TASTE - Is the flavor strong enough? If not, add more Miso, making sure you first mix it separately in a bowl.
Add tofu and scallions. Stir gently.
Serve immediately. Making sure to give each person tofu and scallions. People do NOT eat the ginger coins (unless they really want to).