
Heat a large skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes. Transfer to a paper towel-lined plate; set aside.
In a large bowl, combine chicken, mayonnaise, Greek yogurt, celery, green onion, basil, lemon juice and Dijon; season with salt and pepper, to taste.
To serve, spoon several tablespoons of the chicken mixture into the center of a lettuce leaf, taco-style, garnished with bacon, tomato and avocado, if desired.