Set oven to 400F. Place tomatillos (without the hull) on a baking tray lined with parchment. Roast in the oven for about 10 minutes, or until the tomatillos have blistered and are softer.
Set the Instant Pot or slow cooker on Saute function. If you do not have this option, simply do the following step in a skillet. Once hot, toss in oil, onions, garlic and green bell pepper. Cook for 3 to 5 minutes, until the onions have caramelized and turned slightly translucent.
Add roasted tomatillos and use a spatula to mash the tomatillos and stir everything. As it cooks, add cumin and Green Chile Lime seasoning and continue cooking. Cook for 1 -2 minutes to make a thick, fragrant paste. Turn OFF the Saute function.
Add broth and chicken breasts to the Instant Pot. Add a pinch of sea salt & pepper, then cook. Set the seal to SEAL and Pressure Cook for 25 minutes on High. Alternatively, Slow Cook on Low for 6 to 8 hours, or on High for 4 to 6 hours.
At the end of the cooking cycle, remove the chicken breasts and place in a bowl. Easily and gently pull the chicken apart using forks.
Before adding the chicken back, add green chiles to the Instant Pot. As an OPTIONAL step, use a hand immersion blender to blend the soup to make a consistent, smooth broth. Add the chicken back to the Instant Pot. Cook on low for 10 minutes to allow the flavors to meld.
Garnish and enjoy!