To begin this Hawaiian Oxtail Soup Recipe, you need to preheat the oven to 400 degrees Fahrenheit.
Next, place the oxtails on a baking sheet and cook for 45 minutes in the oven. Be sure to turn it over after 30 minutes so all sides of the oxtail get cooked.
While the oxtail is baking, grab a bowl and soak the dried shiitake mushroom to rehydrate. Use hot water for this purpose.
Remove the oxtails from the oven after 45 minutes and put them in a pot.
Then add the mushroom, star anise, ginger, orange peels, peppercorn, and chicken broth to the broth pot.
Add water to submerge all the ingredients, and set to boil. The amount of water should be about 9 to 10 cups.
Once the broth starts to boil, add the mixture, and then simmer and cook until the oxtails become tender.
Cook and simmer for 3 hours and remove the froth or oil formed on the broth pan.
Use a strainer and strain the broth in a pan to separate the ingredients from the liquid broth.
Serve the oxtail in bowls. Discard any additional ingredients.
Reheat the whole soup again, and once it starts to boil, add the fish sauce and salt to taste.
You can now add the mustard greens for cooking as well.
Garnish the soup with lemon wedges, cilantro, ginger slices, and green onions.