Brush the poblanos with oil and season with salt and pepper. Place the chiles on the grill and cook until charred on all sides, about 10 minutes. Remove from the grill, place in a bowl and cover with plastic for 10 minutes. Remove the skin, seeds and stem and cut into thin slices.
For the onions:
Brush the onions with oil and season with salt and pepper. Place on the grill and cook until lightly golden brown and just cooked through, about 4 minutes per side. Brush with some of the bbq sauce during the last few minutes. Most of the skin should come off on the grill, but if not, take it off when the onions come off the grill.;
For the coleslaw:
Whisk together the mayonnaise, sugar, celery salt, celery seed, vinegar and salt and pepper in a large bowl. Add the cabbage, carrot, onion and scallion and stir to combine, season with more salt and pepper, if needed. Let slaw sit at least 15 minutes before serving.
For the chicken:
Heat the grill to high.
Whisk together the ancho, cinnamon, cumin, brown sugar, 1 teaspoon salt and black pepper in a small bowl.
Season top side of the breasts with the rub mixture, turn over and season the back with the remaining salt. Drizzle with some of the oil and place on the grill, rub side down and grill until lightly golden brown and a crust has formed, about 3 minutes. Turn the chicken over, close the lid and continue cooking until just cooked through, about 6 minutes longer. Remove from the grill and let rest 5 minutes before slicing.
Grill the flour tortillas briefly, just to mark and heat. To build the tacos, fold each tortilla around some of the chicken, poblanos, onions, coleslaw and guacamole.
Fire Roasted Green Chile Guacamole:
Yield:4 to 6 servings
Combine all ingredients in a medium bowl and season with salt and pepper.