Heat 1 tablespoon neutral oil in a large pot. Once hot, add the mushrooms and cook for 8–10 minutes until golden brown. Season with a pinch of salt.
Add the ginger and scallion whites to the mushrooms and cook for 1 minute until fragrant.
Simmer the broth:
Pour in the water and bring to a boil. Reduce the heat and stir in the soy sauce, sesame oil, and dashi granules. Taste the broth and add more soy sauce or dashi if needed.
Add the cubed tofu and coconut milk and simmer for 20 minutes.
Boil the noodles:
Bring a large pot of water to a boil. Cook the noodles according to the package instructions. Drain into a colander, rinse, and divide between four bowls.
Finish the broth:
Taste the broth and adjust the seasonings. Stir in the spinach and simmer for 5 minutes. Turn off the heat.
To serve:
Ladle the broth over the cooked noodles. Sprinkle the minced scallion greens on top. Garnish with chili oil, shichimi togarashi, and sesame seeds if you like. Enjoy!