The exact ingredients of this soup can be adjusted depending on what is on hand. This should produce two large servings for a complete meal.
Use low sodium stock, as the soy sauce adds salt, and extra salt can be added later if needed. Vegetable or mushroom stock should work as well, if preparing this dish without meat.
Place in tea strainer or otherwise ensure final soup does not contain the lemongrass, which can be very hard to chew.
Use salt and sugar free versions of this if possible.
For more heat, add hot peppers or perhaps mustard?
These might be sauted first, in a small amount of grape seed oil, with some salt and pepper, until the water in the shiitake boils off.
Other mushrooms can be used, depending on what is available.
Daikon did not work for me in this soup, despite my otherwise liking daikon. Bell pepper was quite strong in comparison to other ingredients.
The stock can be brought up to a low boil with most ingredients being thrown in as they are prepared, roughly in the order outlined above. If thickening the soup with cornstarch, mix the cornstarch with water first, then slowly add to the soup while stirring. Thin chopped meat will cook quickly, so add it in last, and remove the soup from heat when the meat is cooked.