In a pot, bring the dashi broth to a gentle simmer over medium heat.
In a small bowl, mix the miso paste with a ladle of hot broth until smooth.
Stir the miso mixture back into the pot of broth.
Add the cubed tofu and rehydrated seaweed to the pot.
Allow the soup to heat gently, but do not boil.
Incorporate any additional vegetables like mushrooms or spinach if desired.
After 5 minutes, taste and adjust seasoning if necessary.
Remove from heat and stir in the chopped green onions.
Serve the soup hot in bowls, garnished with extra green onions.
Enjoy your comforting bowl of miso soup!