Heat the 2 Tbs. oil in a large sauté pan over medium-high. Season the chicken with salt and pepper and sear for 6 minutes on each side until cooked through and browned all over. Move to a cutting board and let sit for 5 minutes. Then dice the chicken.
Transfer bell peppers to pan and cook until they just begin to soften, about 3 minutes Remove from pan.
In a food processor, combine the cilantro, lime juice, chipotle peppers and the adobo sauce. Process until smooth.
Add the chicken back and peppers to the pan, along with the chipotle sauce. Toss until combined.
Serve a couple of Tbs. (or more if you’re a freak like me) of the chicken mixture in each lettuce cup and garnish with scallions and avocado!