Pour the water into a pot and bring to a boil. Add the instant Dashi and whisk to dissolve. Turn the heat to medium-low and add the tofu (you can add anything else you want to add now.) Drain the seaweed and add the seaweed to the pot. Simmer for 2-minutes.

In the meantime, spoon the miso paste into a bowl. Ladle about 1/2 cup of the hot Dashi broth into a bowl and whisk with chopsticks or a whisk to mix and melt the miso paste so it becomes a smooth mixture.

Turn the heat off, add the miso paste to the pot and stir well. Taste the soup - if it needs more flavor, whisk in another tablespoon or two of the miso paste. Top with green onions.