Bring to a simmer over medium heat, then reduce heat to low and cover. Simmer on low for at least 1 hour, up to 2-3, stirring occasionally. The longer it cooks, the more the flavor will deepen and develop.
Taste broth and adjust seasonings as needed, adding more soy sauce or sesame oil if desired. Add the miso paste at this time.
When you’re 30 minutes from serving, prepare any desired toppings
Fill a large saucepan or pot with water and bring to a boil and cook according to package instructions – about 4-5 minutes. Drain and set aside.
Strain broth and reserve mushrooms for serving
To serve, divide noodles between four serving bowls. Top with strained broth and desired toppings, such as carrots, pak choy, green onion, or seared tofu. Serve with chili garlic sauce for added heat.