Roast Sweet Potatoes - Preheat oven to 425°F/220°C and line a baking sheet with parchment paper or spray with nonstick spray. Pierce sweet potatoes all over with a fork and place them on the baking sheet. Roast for 30-40 minutes, until tender and a skewer/ knife inserted comes out easily. Remove from the oven and let cool slightly. Peel off the skin, and chop the flesh into small pieces. - If you are short on time, you can microwave the potatoes instead. Pierce the sweet potatoes with a fork all over and place them on a microwave-safe plate. Microwave on high for 5-10 minutes until fork-tender.

Cook Filling - In a large skillet, heat olive oil over medium heat. Add onions, and sauté for 2-3 minutes or until they become translucent. Add garlic, chilies, and spices to the skillet. Sauté for 1-2 minutes or until fragrant. Add mushrooms to the skillet and sauté for 5 minutes or until they start to release their liquid. Add tomatoes, black beans, and vegetable broth and stir to combine. Bring the mixture to a simmer, reduce the heat to low, cover and cook for 10 minutes, stirring occasionally. Add the roasted sweet potatoes and cilantro and stir to combine. - Make sure to drain the canned beans before adding them to the skillet. You can also make the filling in advance and store in the refrigerator overnight. Reheat in a skillet over medium-low heat before assembling the enchiladas.

Assemble and Bake - Preheat the oven again to 375°F/190°C and lightly oil a 9x13-inch (or 3 qt) baking dish. Dip each tortilla into the simmering enchilada sauce, then fill it with a generous 1/4 cup of filling. Roll the tortilla tightly and place it seam side down in the prepared baking dish. Repeat with the remaining tortillas and filling. Use any remaining filling to top the enchiladas. Pour the remaining enchilada sauce on top of the enchiladas and bake for 15-20 minutes or until heated through and bubbly. Serve hot with avocado, cilantro leaves, sliced jalapeños, or whatever toppings you prefer. - Don't overfill the tortillas, or they will be hard to roll and may break. Heating the tortillas before rolling them will make them more pliable and less prone to tearing. If you don't have a baking dish, you can also use an oven-safe skillet or casserole dish.