Heat a large heavy bottom pot with the oil over medium-high heat. Add the sweet potato and onion and cook for about 5 minutes, until the onion is softened. Add the garlic, chili powder, chipotle, cumin and salt and stir to combine.
Add the stock, tomatoes, black beans and quinoa and bring the mixture to a boil. Stir to incorporate. Cover the pot and reduce the heat to maintain a gentle simmer. Cook for 30 to 40 minutes until the quinoa is fully cooked and the sweet potatoes are soft and the entire mixture is thick like a chili. Add the lime juice and remove the pot from the heat. Season with salt as needed.
Garnish with avocado, cilantro, crema or cheese before serving.