Using a large Dutch oven or stockpot, add the olive oil and place over medium-high heat. Once hot, add sweet potatoes, onions and bell pepper. Cook, stirring occasionally, for 4-5 minutes, or until onion begins to soften slightly.
Reduce heat to medium-low. Add all remaining ingredients (garlic, chili powder, cumin, chipotle powder, cayenne, black beans, corn, tomatoes, vegetable stock, lime juice, salt and pepper). Stir and bring mixture to a simmer.
Cover and continue cooking at a simmer for 45-60 minutes, or until sweet potatoes are tender.
Before serving, garnish with sour cream, cilantro, Cotija/feta cheese and toasted sunflower seeds.