Combine wet soak ingredients: buttermilk, salt, garlic powder, smoked paprika and black pepper in a large dish. Place chicken breast cutlets in mixture and refrigerate for at least 30 minutes.
Combine dry dredge ingredients: flour, onion powder, garlic powder, cayenne and salt in a medium bowl.
Coat each breast cutlet in dry dredge then back in wet and a second time in the dredge. Push the chicken into the flour, making sure to really coat the chicken.
Heat oil in a large, wide rimmed frying pan to medium heat. Fry chicken, flipping continuously, until golden brown and cooked to an internal temperature of 160 degrees. Transfer chicken to paper towels or a wire rack to cool. Season with salt and pepper immediately.
Serve on a toasted brioche bun with poblano cream sauce, pickled onions, iceberg lettuce and cilantro.