Heat the avocado oil in a large pot or Dutch oven over medium heat. Add the onion and cook, stirring occasionally, until the edges begin to brown, about 5 to 8 minutes.
Add the garlic and mushrooms, and continue sauteing another 3 minutes, until mushrooms begin to sweat.
Add the remaining ingredients, stir well, cover the pot, and bring to a full boil. Reduce the heat to a simmer, and cook for 20 minutes, or until the soup is very aromatic and the chicken is cooked through.