Preheat an oven to 400 F. Line a baking sheet with foil or parchment paper.
Make the salsa verde. Remove the husks from the tomatillos and rinse them under cold water until the outsides are no longer sticky. Cut the tomatillos into wedges. Place them on the prepared baking sheet with the chopped white onion, serranos, and garlic and toss with the oil. Season with salt and pepper and roast for 20 minutes, until the tomatillos are blistered and the veggies are soft. Transfer the roasted veggies and any juices to a blender with the cumin, oregano, cilantro, and lime juice. Blend until smooth and season to taste with salt and pepper and set aside.
Sear the chicken. Pat the chicken thighs dry and season all over with salt and pepper. In a 5-6 qt dutch oven, heat the oil over medium-high heat. Lay the chicken in a single layer (you may need to do this in batches) and brown for 3-4 minutes per side. Transfer the chicken to a plate.
Simmer the soup. Reduce the heat to medium and add the diced onions and poblanos to the pot. Saute for 3-4 minutes, until the veggies are softening. Stir in the salsa verde, broth, beans and return the chicken to the pot. Cover and simmer for 20 minutes.
Shred the chicken and blend half of the soup. Remove the chicken from the pot and transfer to a plate. Use 2 forks to shred the meat. Meanwhile, transfer half the soup to a blender with the chopped tortillas and blend until smooth. Return the blended soup to the pot and add the shredded chicken. Season to taste with salt and pepper and lime juice and simmer for another 5-10 minutes.
Ladle the soup into bowls and top with tortilla strips, sour cream, cheese, avocado, cilantro, and radishes.