IN a large pot, heat the coconut oil over medium heat. Add the onion and cook, stirring, until softened, about 2 minutes. Add the mushrooms and cook, stirring, for about 3 minutes. Add the garlic and ginger and cook, stirring, until fragrant, about 30 seconds. Add the broth, coconut aminos, fish sauce, and salt. Bring to a boil; reduce the heat to medium-low and simmer, uncovered, for 5 minutes.