Preheat the broiler.
Combine the chicken legs and thighs, chicken stock, olive oil, garlic and chile in a pot over high heat. Season lightly with salt and bring just to a boil. Reduce to a simmer and cook until the chicken is cooked though, about 30 minutes.
Meanwhile, put the tomatoes cut-side up on a baking sheet. Broil until tender and very caramelized, about 8 minutes.
Remove the chicken from the soup and let cool slightly. Discard the skin and shred the meat.
Add the tomatoes to the soup and simmer for 4 minutes, then blend the solids into the stock with an immersion blender. Add the shredded chicken back into the soup along with the onions. Simmer for another 4 minutes. Season with salt and pepper.
Spoon the soup into bowls and garnish with tortilla strips, guacamole, cilantro and sour cream.