In a large dutch oven, combine 15 cups cold water, beef and 1/2 onion and simmer on low heat for 2 hours.
Combine seasoning sauce and set aside.
Remove meat from water and shred into thick strips. Discard water and 1/2 onion.
Mix the fernbrake and shredded beef in a bowl with the seasoning sauce.
In the dutch oven, combine the red pepper oil ingredients and heat over low heat for 5 minutes. Remove to a serving container.
Wipe dutch oven clean and add beef broth along with the mixed items in the seasoning sauce and bring to a boil. Add green onion slices and continue to boil for 3 minutes. Serve hot with red pepper sauce, as desired.