Rinse the rice under running water three to four times until water runs clear.
In a soup pot, pressure cooker or instant pot, add the rice, chicken leg,and minced garlic; cover with the bone broth and four cups of filtered water. Bring to a boil, then turn down to a simmer and cook until rice is broken down to a porridge consistency, about 60 minutes on the stovetop or 30 minutes in a pressure cooker.
Remove the chicken leg from the pot and separate the meat from the bones, cutting the meat into small pieces if necessary. Discard the bone and return the meat to the pot. Add 1 cup filtered water to thin out the porridge, if needed. Bring back to a simmer. Add the shiitake mushrooms to the porridge and simmer for three to four minutes.
Turn off the heat. Add grated ginger, turmeric, and salt and pepper to taste.
Serve hot and garnish with scallions.