- In a large, heavy soup pot, warm the oil over medium heat until it shimmers. Add the onion, and cook, stirring frequently, until tender, 5-10 minutes. Add the garlic, cumin, paprika, and salt, and cook, stirring, for 1 minute. Add the sweet potatoes, stock, chipotle, tomatoes, and beans. Bring the soup to a boil, then reduce the heat to maintain a low simmer and cook, partially covered, until the sweet potatoes are tender but still holding a shape, 20-30 minutes. Stir in the olives. Taste, adding more salt or chipotle if you like.
- While the soup simmers, make the tortilla strips: Heat a thin layer of oil in a wide, heavy skillet over medium-high heat. When the oil shimmers, add enough tortilla strips to fit in a single layer and a big pinch of salt. Cook, stirring and tossing occasionally, until golden and crisp, 2-3 minutes. Remove and let drain on paper towels. Repeat with the remaining tortilla strips and oil.
- In a small, non-reactive bowl, stir together the diced red onion, lime juice, and a big pinch of salt. Let sit until the soup is ready to serve, at least 5 minutes.
- Just before serving, stir in the chicken. Ladle the soup into bowls Garnish with a nest of tortilla strips, avocado slices, queso fresco, cilantro, and olives. Sprinkle with the pickled red onion and drizzle the lime juice over the top.
- Extra soup keeps well, refrigerated, for up to 3 days.