Step 1: Prepare the Ingredients

1. Peel and slice the daikon radish into thin rounds or half-moons.
2. Chop the onion, garlic, ginger, and carrot.
3. Slice the mushrooms (if using) and set aside.

Step 2: Sauté the Aromatics

1. Heat a large pot over medium heat and add the sesame oil.
2. Sauté the onion, garlic, and ginger for 2-3 minutes until fragrant.

Step 3: Add the Vegetables

1. Add the sliced daikon, carrot, and mushrooms to the pot.
2. Stir well to coat the vegetables with the aromatics.

Step 4: Add the Broth and Seasonings

1. Pour in the vegetable or chicken broth and water.
2. Add the soy sauce, fish sauce (if using), and a pinch of salt and pepper. Stir to combine.

Step 5: Simmer the Soup

1. Bring the soup to a boil, then reduce the heat to low.
2. Cover and simmer for 20-25 minutes, or until the daikon is tender.

Step 6: Garnish and Serve

1. Taste and adjust seasoning if needed.
2. Ladle the soup into bowls and garnish with chopped green onions and fresh cilantro or parsley.