Step 1

Heat oil in a large saucepan over medium-high. Cook yellow onion, stirring often, until very tender and just beginning to brown, 6–8 minutes. Add garlic and cook, stirring, until very fragrant, about 3 minutes. Add cumin and fennel and cook, stirring, until fragrant, about 1 minute. Add chicken broth and chiles and bring to a simmer. Cover and cook, maintaining a gentle simmer, until chiles are rehydrated and very soft, 25–35 minutes.

Step 2

Pour soup into a blender (reserving saucepan) and add beans. Carefully purée until smooth. Return soup to saucepan and bring to a simmer over medium heat. Season with salt and pepper. Stir in chicken, if using.

Step 3

Place corn chips in serving bowls and top with stew. Lay avocado on top, if using. Add a dollop yogurt, then top with radishes and white onion. Sprinkle with cotija.