In a large heavy-bottomed pot over medium-high heat, heat the olive oil. Add the chopped onion, sweet potatoes, diced green bell pepper, and minced garlic. Stir to combine, and cook until the onions are translucent and the vegetables begin to soften, about 5-7 minutes.

Add the chili powder, smoked paprika, ground cumin, dried oregano, salt, and black pepper to the pot. Stir well to coat the vegetables evenly with the spices. This helps to toast the spices and bring out their full flavor before adding liquids. I always find that giving the spices a quick toast like this gives the chili a deeper, richer taste.

Pour in the low-sodium vegetable broth, then add the rinsed and drained black beans, fire-roasted diced tomatoes with their juices, and chopped green chiles with their juices. Stir everything well to combine and bring the mixture to a boil.

Cover the pot and reduce the heat to maintain a gentle simmer. Cook for 30-35 minutes, stirring occasionally, until the vegetables are tender and the chili thickens to your liking. This slow simmer helps all the flavors meld together beautifully.

Ladle the hot chili into bowls. Top each serving with diced avocados and fresh cilantro leaves, if desired, for a refreshing and creamy finish. For an extra burst of flavor, I sometimes add a squeeze of lime juice just before serving.