Preparation

1. Marinate the chicken: In a small bowl, whisk together the mezcal, lime juice, orange juice, hot sauce, and 2 teaspoons kosher salt. Place the chicken breasts in a large resealable plastic bag and pound with a mallet or the bottom of a small saucepan until they’re about ¾ inch thick. Add the marinade and knead to coat the chicken. Refrigerate for at least 30 minutes and up to 4 hours. 
2. Make the chipotle crema: In a small bowl, stir together the sour cream, mayonnaise, lime juice, and adobo sauce. Season to taste with salt. Refrigerate until ready to use (the crema can be made up to 2 days ahead). 
3. Heat a HexClad Hybrid 12" Fry Pan over medium heat and add 2 tablespoons oil. When the oil begins to shimmer, add the onions and cook, stirring, until they begin to soften, about 3 minutes. Add the bell peppers and cumin and a generous pinch of salt. Cook, stirring occasionally, until the peppers and onions are softened and browned in spots, 5 to 6 minutes longer. Add about 3 tablespoons of the marinade to the pan and cook, stirring, until the liquid has evaporated, about 2 minutes. Scrape the contents of the pan to a serving platter.
4. Remove the chicken from the marinade pat dry with paper towels. Add the remaining oil to the pan. Add the chicken to the pan and cook, turning the chicken every minute or two, until well browned and cooked through, 10 to 12 minutes. Transfer to a cutting board and let rest for at least 5 minutes, then slice across the grain into ½-inch strips. Transfer to the serving platter. 
5. While the chicken rests, warm the tortillas. Wipe out the pan and return to medium-high heat. Add 1 tortilla and cook for 30 seconds per side, then transfer to a plate and cover with a towel to keep warm. Repeat with the remaining tortillas. 
6. Serve alongside the cilantro, queso fresco, sour cream, and guacamole, if using, for garnish.