In a large bowl filled with hot water add dried chiles until the chiles have softened about 10 to 15 minutes.
Blend the softened chiles with torn tortilla pieces, fire roasted tomatoes, and 1 cup chicken broth in a blender. Blend until smooth.
Select Sauté on the Instant Pot and warm the oil. Add the onions to the pot and cook, stirring occasionally, until tender and translucent, about 3 minutes. Stir in garlic for 1 minute.
Lightly sprinkle salt over chicken breasts, and chicken thighs.
Add the chicken, tomato mixture from blender, and remaining chicken broth, and give everything a good stir.
Lock the lid in place and turn the valve to Sealing.
Press the Manual/Pressure Cook button and set the cook time for 20 minutes at high pressure.
Let the steam release naturally for about 10 minutes, then turn the valve to Venting to release any residual steam.
Carefully remove the lid and, using a slotted spoon, transfer the chicken to a bowl. Using 2 forks, shred the chicken.
Add shredded chicken back to pot and season with salt if needed.
Ladle soup into bowls and serve with tortillas strips, avocados, a squeeze of lime juice, and your choice of toppings.