In a food processor, purée the cilantro, green onion, pepper and garlic. Season with salt and pepper. Add the oil and lime juice. Mix well. Keep in the refrigerator until ready to serve.
Preheat the grill, setting the burners to high. Oil the grate.
On a work surface, season the chicken with salt and pepper. Sprinkle with the chili powder. Grill for 4 to 5 minutes on each side, or until the chicken is cooked through. Let cool. Cover with plastic wrap and refrigerate for 1 hour, or until it is completely chilled. When ready to serve, slice the chicken.
Place the sliced chicken in the middle of a large serving platter. Arrange the lettuce, tomatoes, avocado, beans and chips around the chicken. Season with salt and pepper.
Serve with the dressing and, if desired, sour cream.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.