Place a large saucepan over medium-high heat. Add olive oil, then toss in the onion, garlic, and jalapeño. Cook until the onion becomes soft and translucent and the jalapeño starts to break down.
Season with salt, pepper, oregano, cumin, and chipotle powder. Stir well and let the spices toast for 1–2 minutes to deepen flavor.
Pour in the fire-roasted tomatoes and chicken stock. Stir and bring the soup to a boil. Once boiling, reduce the heat and simmer for about 30 minutes.
Turn off the heat and blend the soup using an immersion blender until smooth (or partially, if desired). Taste and adjust seasoning.
Stir in black beans, frozen corn, and shredded chicken. Let heat through for 5 minutes.
Meanwhile, fry tortilla strips in a small skillet with a thin layer of oil over medium-high heat, about 30–45 seconds per side. Drain on paper towels.
Ladle the soup into bowls and top with shredded cheese, avocado, cilantro, tortilla strips, and a squeeze of lime. Add jalapeño slices if desired. Serve immediately.