Heat olive oil in a medium sized pot. Add onion and green pepper and cook until softened, about 5-8 minutes. Add garlic and cook for an additional 1 minute.
Add chicken broth, green salsa, cilantro and chicken breasts. Your chicken should be fully covered by the liquid. Bring to a boil, reduce heat to a medium low and continue cooking covered until chicken is cooked through about 10-12 minutes.
Pull out chicken, set aside. When cool enough to handle shred using two forks. While the chicken is cooling, pour half of the soup (including all of the cilantro) and the avocado into a blender. If needed, do this in two batches.
Return the blended soup to the pot, add in the shredded chicken. Taste and adjust seasoning as desired.
For the tortilla strips, heat 2 tbsp of neutral oil to a saucepan. To make sure the oil is hot enough, drop one tortilla strip in to test. It should sizzle immediately.
Once hot, carefully add the remaining tortilla strips into the pan in a single layer. When golden brown, flip tortillas about 1-2 minutes per side.
Remove from the pan and place on a plate lined with a paper towel. Immediately sprinkle with salt.
Garnish bowls of soup with sour cream and tortilla strips. Enjoy!