Heat 1 tablespoon of the oil in a large Dutch oven or soup pot over medium heat.
Add the chicken and fajita or taco seasoning, and brown until cooked through, about 5 minutes.
Remove the chicken to a plate.
Add the remaining 2 tablespoons of oil to the Dutch oven, and saut the onions until they are translucent, about 4 to 6 minutes.
Add the garlic, jalapeos and poblanos, and saut for about 1 to 2 minutes, or until fragrant.
Pour in the chicken stock and the tomatoes and bring to a medium boil, cooking for about 3 to 5 minutes.
Add the cooked chicken, cilantro and lime juice and stir.
Season with salt and pepper to taste.
Serve the soup topped with avocado, lime and cilantro, if desired.