In a cast-iron pan over medium heat, toast spices until aromatic, about 1 minute, tossing frequently. Turn off the heat and let cool for a few minutes, then transfer the toasted spices into a spice bag and set aside.
Step 2
In the same (now-empty) pan, toast daikon, onion, and ginger until charred on all sides, 3 to 5 minutes.
Step 3
Fill a 5-quart pot with 12 cups of water. Place all the soup ingredients and the spice bag in the pot and cover it with a lid.
Step 4
Bring the mixture to a rolling boil, then lower the heat and simmer for an hour.
Step 5
Once it's ready, strain the broth, and season to taste with umami seasoning, plus salt as needed.
Step 6
To serve, divide the noodles into four bowls. Top with a few ladlefuls of broth, then with herbs and other garnishes of choice. Don't forget to squeeze on some lime juice! Serve warm and enjoy.
