Season chicken breast liberally with spice mix. In a heavy bottom cast iron pot, heat canola oil on medium heat until shimmering. Sear chicken breast for 3-4 minutes per side, until golden brown. The goal is just to get a good sear on the chicken, not to cook it through.
Place rack at the highest level in oven. Turn broiler to high. Remove husk from tomatillos and stems from poblanos. Rinse and pat dry, then place on a baking sheet lined with parchment paper. Broil on high for 5 minutes per side, until tomatillos and poblanos become blistered and start to release their juices.
Once cooled, add tomatillos and poblanos to a high powered blender, along with fresh cilantro, garlic and chicken broth. Blend to desired consistency.
Pour pureed mixture back into the cast iron pot. Bring to a boil, then add chicken breasts, cover and reduce to a simmer. Cook for 20 minutes. Remove chicken breasts and shred, then return to the pot. Taste and adjust seasonings.
While the soup is simmering, add 1/4 cup canola oil to a frying pan over medium heat. Cut corn tortillas into 1 inch thick strips. Once the oil is hot, fry strips in batches for 15-20 seconds per side. Transfers to a paper towel-lined plate to remove any excess oil. Sprinkle with salt while the strips are still warm.
To plate, even distribute soup into bowls. Top with sliced avocado, fresh cilantro, cream, and tortilla strips.