Preheat the oven to 375 degrees . Arrange the tortilla strips on a baking sheet in a single layer; spray with cooking spray. Bake until deep golden, about 15 minutes. Season with salt.
Meanwhile, in a soup pot or dutch oven, heat 3 tbsp. oil over medium heat. Add the tortilla squares and cook, stirring, until browned, 2 to 3 minutes. Add the remaining 1 tbsp. oil, the yellow onion, garlic, cilantro, bay leaves, chili powder and cumin; season with salt and pepper. Cook, stirring, until the spices are toasted and the onion is softened, 7 to 8 minutes. Add the stock and tomatoes and bring to a boil. Add the chicken and lower the heat to a simmer until ready to serve.
Peel, seed and dice the avocados. Place some at the bottom of each soup bowl and douse with a healthy squeeze of lime juice. Pour the soup into the bowls. At the table, top with the red onion, baked tortilla strips, jalapenos, queso fresco and sour cream. Serve with the remaining lime wedges.