Heat the oil in a pot over medium heat. Add the yellow onion and sauté for about five minutes or until soft. Add the mushrooms and cook for another five minutes, stirring occasionally.
Add the taco seasoning along with tomato purée, broth, and black beans. Stir, cover the pot with a lid, and let it simmer for about five minutes.
Season the mixture with salt and pepper. Add the quinoa to the pot and stir. Cover with lid again and let simmer on low heat for about 15 minutes or until quinoa is cooked through. Stir the chili occasionally.
Divide the chili evenly between bowls. Top with green onion and enjoy!