Vegan Sweet Potato Chili

Name: Vegan Sweet Potato Chili
Ingredients: 2 tablespoons extra-virgin olive oil; 2 dried ancho chiles (1 ounce), stems removed, split lengthwise, and seeded; 1 medium onion, chopped (1 ½ cups); 3 cloves garlic, minced (1 tablespoon); Kosher salt and freshly ground pepper; 2 tablespoons tomato paste; 2 teaspoons chili powder; 1 teaspoon ground cumin; ⅛ teaspoon cayenne pepper, optional; 1 ½ pounds sweet potatoes (2 medium), peeled and cut into ½-inch pieces (4 cups); 1 (15-ounce) can black beans, drained and rinsed; Sliced avocado, thinly sliced scallions, and crushed corn chips, for serving