On a large pot, boil the beef and bone broth with black peppercorn, parsley, thyme, bay leave, carrots, celery, and garlic for 1 hour.
Meanwhile, thinly slice the onions and heat the dutch oven on low.
Melt ghee butter or heat avocado oil before adding onions. Sauté onions on low-medium heat for 30 minutes.
Add tapioca starch to the onions and mix well.
Take 3/4 cup of the boiling broth and add onto the onions. Scrape the bits and stir for a minute.
Drain the broth into the dutch oven with a mesh strainer.
Season the broth with fish sauce, coconut aminos, and salt. Simmer for 30 minutes.
Turn on the oven to broil.
Layer soup with AIP mozzarella cheese or vegan cheese.
Broil for 5 minutes until cheese melts.
Let it cool and serve.